I wanted an XY controller to control CC1 and CC11 for more realistic playing in of MIDI parts. I bought a Korg NanoPad2, which has a small XY pad built in, but was disappointed with its limitations. I am now using that for what it was designed for, programming in drum and percussion parts.
The good news is I just setup the Lemur app on my iPad ($49.99) and am using it to control Logic and Kontakt on my Mac Pro. All I can say is, wow! What a fantastic tool. My first project in Lemur was to design a CC controller for Sample Modeling Brass. It works flawlessly.
The Lemur app is usually used wirelessly, but since my Mac Pro doesn't have an air card, I had to spend another $69 for a Line 6 MIDI Mobilizer II to hardwire my iPad to my MOTU MIDI Express interface, but for just over $100 to have Lemur fully functional on my iPad is a great deal considering what the Lemur hardware units went for a few years ago.
So if anyone is interested in having complete control over their DAW, Samplers and Libraries, I recommend checking this out if you own an iPad.