So I plopped down the measly $20 for Ampkit+, and have been enjoying it quite a bit. It comes with the following amp models:
Colonial (Marshall JTM45)
I also added on the Budda SD30, because A. it was only .99, and B. it sounds damn good.
Effects are the standards: chorus, echo, flanger, noise gate, TS-type drive.
You can save different presets, and what's nice about AmpKit+ is that it actually includes the channels originally on the amp. For example, the SD30 has two channels, so they're both there, but the Colonial only has one, so that's all there is. The 3120, on the other hand, has all three channels. Just like real life, only the clean and crunch are usable.
The modeling itself, IMO, is pretty damn good. They just updated the modeling on it within the last week, to the point where it requires an iPhone 4, iPT 4, or iPad 1 or 2 for the higher res. Whatever it's doing, it needs the extra power of the A4.
I'd definitely say this is better than any Line 6 modeling except the HD stuff, better than what's in GarageBand, and significantly better than Amplitube on iOS. With the Apogee JAM as the interface, there's just no comparison.
I think it'll be a short time before I either stuff the Pocket POD in the drawer, or sell it altogether. Having everything in the iPad or iPhone is very convenient, and sounds great. For $20, this app is definitely a good deal.