One interesting thing I've been experiencing lately is that I have a 3.0 GHz Prescott machine at work with 1 GB of RAM, and a 4200+ at home with 1 Gig. The difference I see, running the same large collection of apps on both systems, is that the Pentium 4 starts choking after awhile. In fact it actually quits allowing tasks to execute after awhile until I close out a couple other processes. Now, this might be a weakness of the OS (XP Pro on both machines), but I never run into that kind of roadblock on my dual-core Athlon machine.
So I would absolutely get the 3800+. They do OC like crazy if you want to do that, and the power/price ratio is unbeatable.
(I of course ignore CPUs that you could fry an egg on even if their prices are artificially cheap. I remember when we used to sue Asian companies for dumping semiconductor products into the US market. Wonder if we could sue Intel for dumping sh*t processors into the market? Just wondering.)