I just picked up my second X-keys Pro, once you get it figured out you'll LOVE it.

Here's what I recommend:

Use the Hardware Mode programmer, as that way you can use it through a keyboard broadcaster if need be. If it didn't come on the CD that came with the device, you can easily download it from their website under the software section.

I find that Alt combinations are a little unreliable via USB so I tend to stay away from them. It's just as simple to set up using, say, CTRL-SHFT-A and so forth in addition to just CTRL-A and so on. You really don't have to use ALT at all.

Some folks here have found that USB is unreliable through a hardware caster, but honestly I have had few problems with my setup.