I am having great success migrating from a traditional keyboard to a midi controller keyboard using Mainstage software on my Mac for the sounds.
I thought I'd share because maybe this set up would benefit others.
It is a benefit to me compared to my old set up because I was using an aging synth (Alesis QS8). For $220, I picked up an M-Audio 88es, which is a full sized semi-weighted USB keyboard controller and am hooking it up to my Macbook which is running Apple's Mainstage software ($30). The sounds in it are amazing and are up there with any modern traditional synth in my book. Plus it is easier to organize sounds on the Mac. I run all of this out to an M-Audio Fastrack USB audio interface that cost only $50. The most expensive piece of gear is the Macbook itself.
The midi controller is a fraction of the weight of my Alesis and is a breeze to take to gigs. The one down-side I see is that this locks me into the Apple hardware (I haven't found anything close to Mainstage for the price in the Windows world). Should my Macbook ever die, I'll have to buy another one unless Ipads come up with USB interfaces for use with my midi controller.... Perhaps they already exist?
Glad it's working well! There are a couple of iPad MIDI interfaces out there, including this one:
I believe Line has one as well. Can't comment on how well they work, but I've often thought that a lightweight controller with an iPad/iPod would be an ideal mobile rig.
Check out iConnectivity.com. I have the iConnectMidi, it's great!
The line 6 midi is great.. And iRig has been in this game from the beginning of iOS.. I'm getting ready to review both the iRig stomp and the Irig blue board (the first ever wireless midi foot controller for iPad) ik multimedia is sending them to me.. Great stuff for portable systems and cutting the laptop out of the equation
I have an IPAD and I bought a cheap camera connection kit from amazon to hookup usb devices. I have a powered USB hub with an axiom 25 midi controller, a Peavey PV-14 USB mixer, and a FCB-1010 foot controller all running into my IPAD and everything is working really well especially with the Loopy HD app. The main thing to look for is if the USB device is class compliant.
The camera connection kit is only like 6 bucks.
My only complaint is that it does not charge the IPAD but as long as you do not leave the camera connection kit plugged in when you are not using it the battery lasts a while.