Im a bass player thats come fairly late to the whole iOS thing but have now enthusiastically jumped into the world of virtual amps. Ive tried several of the apps that are out there but have developed a heavy preference for PocketGK.
PocketGK is very well thought out for the average bassist - Id say it provides about 90% of my dream list for an app. Tone is great, the play along and looper features are useful practice tools and the built-in tuner works well. The only things on my wishlist for PocketGK are a few of the typical effects bassists tend to use - a compressor, fuzz, distortion and possibly chorus would be great to have as in-app purchases.
Also, iRiffPort is the way to go for an interface - I tried a few of the audio jack interfaces and was very disappointed on poorly they worked for bass. iRiffPort gives me a great low noise way of accessing PocketGK on my iPhone and iPad. iRiffPort also works well with the new Lightning to 30 pin adapter (my iPad is Lightning equipped.) Hopefully well see more interface products from Pocketlabworks - a stompbox interface to give an easy, durable way of jacking PocketGK into a pedaltrain would be great for live performance.
Pocketlabworks has a winner here!
HeavyDuty Ken about PocketGK - Bass Guitar Amp