Yes Accordianist - You can load a number of user styles (called patterns to avoid confusion)in addition to the 172 internal XD styles. The amount you can load depends on the complexity and amount of instruments that are used in them. If I load some of my old MS styles I get far more as these only had 3 acc voices instead of the 5 on the XD.
You also have a certain amount of flexibilty with editing the internal styles. Although you can't change the patterns of each of the accompaniaments you can change volumes, instruments, drumsets, effects, speed etc and store these as the new factory preset within the XD. This makes a lot of the styles more useful to me for gigging as some styles can get a little busy which is great fun but could make songs sound similar when the same pattern is used. There is a restore function which will get you back to factory settings at any time
Another good feature is the lock function which enables you to have the same drum and/or bass and/or any of the acc. routines play on all variations. This can give more variety on the internal and user styles than you would otherwise have.
You need to go to places like Yahoo who have several groups you can join such as Solton Ketron and MS40. There are many accordion players here who have and use MS40, X4 or XD3 modules who can also answer other more specific questions (relating to accordions).
With regard to demo's, you can get these off the net - also listen to SD1 demo's - these are very similar. - BUT - You really need to listen to any instrument and play if you can before you buy. Having said that, the XD is really cheap here in Europe and, even if you buy without seeing it in the flesh (as they say), you're not taking as much as a chance than if you buy a Yammie or Technics as you are not paying for a keyboard and speakers you dont need.
The Ketron Modules have a special accordion mode and will allow you to do things simply not possible on other makes - I know two accordion players with these and as far as they are concerned you cannot touch them.
One other point is that some people seem to have an issue with Ketron reliability. I can only tell you that I had an MS40 for nearly 8 years and the XD3 without any problem - but - If it's important and your living or reputation depends on it then you should have some contingency. Of course this applies to all makes of keyboards and other equipment.
Hope this helps - If you put your e:mail into your profile I could send you styles to try when and if you get the Ketron or email me direct.
Regards - KF