I personally don't have one yet, but from the reviews all over the Internet, the 3800+ X2 is a great CPU. It combines the ability to play games and much improved multitasking capability.
If you have about $320 to spare, it's one of the best dual-core processors out there. Very good performance for the price. Basically two 3200+'s with 512k L2 Cache per core. Try to get the Toledo cores if you can...they overclock better, unless you're anti-overclocking, which in that case the Manchester core would be suitable for you (which is the majority of the X2 3800+'s).
I also searched it up on PriceGrabber for you. The cheapest is $315.00, although you have to plug in your zip code for the exact shipping and handling added in.
I would say definitely worth getting. It's at a reasonable price, and performance will improve not decrease, as software starts to be written to take advantage of dual-core CPU's, so yeah, if you can afford it, I'd say get it.