I'm using the Millenium edition of ViaVoice. Despite the glitches (particularly in Trillian) and the fact that I have very little idea what I'm doing, I'm very impressed with it. If a three-year old version I picked up for free works this well for a user without a clue, a new version, trained and being used by a fluent user seems like it would be great!
Smoochy, I have arthritis too, which is why I picked this up. I'd definitely say it's worth it, but it takes time to train and learn. I gave up for the evening (don't need to frustrate myself with it) but it's a handy tool.