Definitely nice... I do a lot of audio software creation and dual core has been an instant performance boost as the audio engine I use (SuperCollider3) runs on a core and my game / timing loop runs on another and blamo no audio glitches / drop outs during intense use on the timing loop. Where as before on a single core I had to be really sensitive to not hog the timing loop for say loading a game level (Auriga3D). I couldn't play glitch free audio and let the game engine chug along full speed (again during loading). During gameplay things were fine single core, but dual core clears all of this up and can do audio and intense use of a timing loop synchronously with no drop outs. mmmm....
I'm probably going to pimp out my 939 AMD system with the last dual core processor of that line soon... Holding off to K8L maybe for a full upgrade.. Got the 1900XTX though a month ago or so.. mmm...

I'm really waiting for a tablet PC that has a graphics accelerator as well.. I'm running a large scale surround system on a thinkpad w/ firewire card and RME Fireface this weekend.. So portable.. Considering 3 years ago my setup consisted of a Mac and PC desktop networked with two CRT monitors.. mmmm... tech life goes on...
I just got the Sidekick3 too and oh my gosh is it easy and fun to program for and is quite a nice environment for creating games; there are nice features such as fillTexturedPolygon primitive that will make doing more interesting engines possible; I haven't really hit it for performance yet though have a simple tank game functioning. I hope to squeeze out some games for the SK3 in my "spare" time.. That and get the SK3 controlling my surround sound software so I can drop the volume on bad DJs/performers... ;P