i have a 1st-gen iBook (160Mb ram, 233MHz processor).  

i have loops/grooves that i'd like to overlay w/vocals and other instruments using the tascam...

will my iBook work well w/a Tascam US224?

realprof.

I have a 224 sitting right next to my iBook (600MHz) as I type this. It's OK and yes, it works well enough at getting audio into my Mac, but I don't like it as much as Digidesign's Mbox. Yes, the Mbox costs more, but it's a much cooler product. No Midi, though, so there's a point scored for the 224. But the version of Cubasis that comes with the 224 is rubbish! You get Pro Tools LE 5.1.2 with the Mbox, which is much better. Neither interface worries about the speed of your computer - that's only going to be a restriction for you and how much audio your Mac can handle.