There was a recall for some but not all for the PCM, but I don't know the details because none of mine were affected. IT was a recall though, so whatever Vibe you buy, GM will do the recall work if you are the original or 100th owner of the car if it hasn't already been done.
The base and AWD models of the first gen vibes (03-08) had a Toyota 1ZZ engine, and the 03 1ZZs were rated at 130 HP. (actually, because of different exhaust, the AWD model was only rated at 123 HP) The first gen Vibe GT's had a Toyota 2ZZ engine, and at least the 03 2ZZs were rated at 180 HP. From my base owner perspective, the important differences are that the 2ZZ requires huigher octane (and higher $) gas, and that the GTs only ever came with a manual transmission. The extra power of the 2ZZ is what is called "lift", at high RPMs you get a surge of power. Since I like buying cheaper gas, and now prefer an auto tranny, and never get RPMs up to where I'd ever hit lift, I filtered out the GTs the last time I was shopping for one.