I didn't realize it initially, but the PSPgo has a 3.8" screen compared to the regular PSP's 4.3" screen (with the same 480x272 resolution). I'm not sure why that was necessary, but it makes the PSP 3000 seem like a more attractive option.
I might not get either one. I still don't see the games I would want to play available for download (mainly shooters - Gradius, Salamander, R-Type, etc.), and if they aren't made availble at the PSPgo's launch, I'll probably abandon the whole idea. I'm happy with my DS Lite, anyway.