I'm now on day 3 with my new Surface Pro and I now have some reasonably informed thoughts on it so far.
I'll start off with the negatives, just because.
Battery Life
Obviously this is the biggest weakness with the device. I would dearly love this device to have 6+ hours of battery life, but I seem to be getting just over 4 hours with general use. It's on par with my HP Touchsmart TM2 convertible tablet. That makes it serviceable, but It is something I would love to see improved.
They have been hinting that they may release some soft of external battery option at some point. That may help. We'll have to see what/how they implement it.
Price
There is no way around it. It's an expensive device. I'm actually fine with the cost of the device itself. For what you are get getting, It's not that far off from a laptop with similar specs.
That said, It really, really, should have come with one of the type covers.
Disk Space Available
Simply not an issue for me. While I did get the 128GB version, I never considered the whole usable space thing an issue. This is a full windows device, and no one would have ever complained about a recovery partition and the size of the OS if they were to purchase a laptop or ultrabook.
Performance
In a word, excellent. It boots in seconds and my desktop apps fly.
Photoshop CS6 loads in 5 seconds and I don't see any performance issues when editing a photo.
I wasn't expecting a gaming machine when I got the Surface. I was actually surprised when I saw that I could run Civ5 reasonably well on it. I even am able to run Everquest 2, with fairly low settings. I don't see myself ever gaming on this device, but I am pleased that it's able to do so even if somewhat limited.
Pen Support
There are a few issues here. The pen generally works, but they need to get the proper Wacom drivers working to support more applications.
For note taking it works very well with One Note. Palm rejection seems to work very well. I haven't had nearly as many issues in this device as I have in others like the HP Touchsmart or Asus EP121.
General Hardware
I think Microsoft deserves some credit here. They could have gone with a number lesser features like many others have, but they didn't.
USB 3, Bluetooth 3.0, mSata, Dual band WiFi rather than just 2.4 ghz that most internal wifi cards seem to give. They could have cut a few corners here, but they didn't.
The device also feels solid. It doesn't feel cheap at all.
Type Cover
I went with the $130 type cover. While it was way to much money for what you get, it's really outstanding. I find it very easy to type on, and I can maintain a very reasonable speed when working on it. It is very thin and light for a keyboard. surprisingly so.
It attaches easily, it doesn't add too much thickness overall when used as a cover. Closing it puts the Surface to sleep as if it were a laptop. Flipping it under disables it so you don't have to take it off if you want to quickly use it in tablet mode.
These are my initial thoughts on the Surface Pro so far. I have been making a point to use it at work to take notes and complete check lists in PDF format. I also do my personal e-mail, surf, listen to music as well. It's the best tablet PC I have owned so far.