I have a macbook pro, I have a need for large storage. I have 3 really easy options.
1) External USB drive (cheap, fast enough for most everything but running applications or streaming video (although it does that ok as well)
2) Firewire 400/800 external drive (for that extra speed)
3) If I just need that performance, well I've got that covered too. I can get a sata card. In fact right now I"m looking at getting a sata card for my macbook pro so I can hook it to a small raid 5 storage device for my 'must keep' data and backups.
My desk is cleaner now, I don't have a giant case under there to dust. My office is MUCH quieter. The macbook pro makes my old amd x2 4400 sound like a wind tunnel. And I can get up and go when I need to. In fact, the ONLY thing my mac can't do as well as my last setup is gaming. But as I gave up windows awhile back, my gaming was limited to cedega/wine anyways, so the only difference is I can't play with the graphics as high as I could with my old desktop. However, some games which I used to have to emulate actually have mac versions (warcraft 3/WoW/NWN2/Civ4/etc) so I would say the gaming is better then my old custom built desktop.
I used to think I "HAD" to have raid 5 desktop with a TB of storage. I've come to find out that I was throwing my money away in the wrong places. Sure, my last PC build was 1000.00 less then my new mac, but the experience is not as nice. I can not ever go back to a desktop computer again, even if I decide to go back to linux. Simply put, having a brand new high end dell laptop at work, a midrange ibm laptop at home (my wifes) and my new mac, the macbook pro is the best example of craftsmanship I've seen in a long while. I've even found the keyboard easier to type on (I bought a bluetooth apple keyboard and mouse).
But I've realized that I have network storage, it is good enough for anything I need to keep over 100 gig. There is no reason my music needs to be on my hard drive, no reason my videos need to be on my hard drive, no reason all my old documents need to be on my hard drive. If it is being archived, then I archive it off my hard drive. I keep an old small machine downstairs with a nice huge raid setup to hold all that. For my more immediate storage, I have a 4 gig usb stick and a 500 gig usb drive and as stated above, i'm looking at a sata card to give me faster access for doing images and time machine (and possibly killing the need for network storage). Plus, by going this route, my data is now portable. I can ssh in from work and listen to my songs, I can easily start torrents from anywhere, etc. Simply put, my life is better.
Beyond that, I have discovered tools I have not found the match of in windows or linux. Things like textmate for example. It is the most amazing editor I've ever used. I can't think of anything anywhere that comes close to it. Xcode is also brilliant and much more my style then visual stuido or anything on linux. On the pure linux side, I can now use dreamweaver and photoshop if I desire (I wouldn't if gimp didn't require X on mac). I find iTunes much better then it is on windows (and much more stable). After syncing iCal with google calendar I've become addicted to that mixed with apple mail as well. I've become a complete junky of quicksilver and fallen in love with how integrated everything is with that and growl. Garageband has brought new life to my guitars that used to sit in the corner doing nothing. And expose, dashboard, and spaces are lightyears beyond what I've experienced in windows (but linux does spaces a lot better imho)
Beyond that, almost every single applications I can think of that I use on windows or linux either exists on mac, or has a nicer replacement. There is one exception however, I hate transmission. I miss uTorrent. But I plan to do something about this and start work on my own libtorrent based cocoa bittorent client. (If I can get myself to stop taking contract work).
Finally, I've started to get annoyed with windows and linux when i use them. I find myself hitting alt-c/v when trying to copy and paste because I've gotten so used to the command key. I've gotten frustrated in the lack of integration and consistency between applications. I also get really frustrated with the trackpad on my dell laptop. It is inferior to my macbook in so many ways. (Hell the whole laptop is, same specs only with intel video and it is fatter, heavier, hotter, the screen brightness is not constant, and it is nosier).
My wife has already told me that when we replace her aging computer that we will be getting her either a iMac or a macbook (she does not game at all and says she will be fine with low end graphics of a macbook). I am thinking she will be getting a macbook and probably within the next 6 months. I have also shown it to my mom who fell in love with it. She has constant problems with her computer (usually because she is not the most security conscious person). The mac will help mitigate some of her risk (her husband won't be installing tons of those random internet games on it) and she found the interface easier to use. She was able to do tasks on my mac that she normally calls me for help with on windows. My grandmother is also someone I have suggested the mac to. She was a windows 98 user who used linux (managed by me) for a while and recently got a new computer (I think about 2 years ago) and went back to windows. When she is ready for a new computer, I'm going to suggest a macbook. Not because she has trouble with windows, but because the macbook is better built then most of the dells out there and she has been talking about going to the laptop format.
One last thing. When I owned a windows machine, I spent a good deal of time maintaining and customizing that machine. I was always looking for faster antivirus, or better anti-spyware, or tricks to improve the speed. When I moved to linux, this became even greater. I would spend over 60% of my time just 'improving' things by customizing my desktop, writing scripts to automate tasks, recompiling software to make it 'run faster'. Switching distros to get a 'better experience'. It was a treadmill I was sucked into. I just didn't feel happy with my system. It seemed like the purpose of the computer was to maintain it and not use the software on it. Now with my mac, I sit and think, "what would I change?". The answer is a much shorter list. I love the mac as it is out of the box. The only tweak I've done so far is to set the dock to be a flat dock. The rest of the things I want to change are just applications that I think could be done better. Which means I'm doing actual useful work on my computer! I've gotten so much more done in the last few weeks then I have ever gotten done before. Maybe it is a placebo effect, I'm not sure. I can tell you that my boss has mentioned that I must be in love with my computer because I'm turning in work much faster then in the past. I think it is because in the past I have found laptops to be annoying and sitting in my office to be tiresome. But the macbook pro is great and I spend a lot of the time sitting outside on my porch doing work or sitting with my wife by the tv doing work. Combine that with textmate and I'm as happy as I've ever been.