So, riding the trained dressage horses has been great. They are really nice horses, kind in addition to well-trained, so everything just seems easy. Of course, I am absolutely sure that Jessica is being much less demanding of me than she would be of someone who actually had the first clue about dressage. Still, this winter while Tag has been at his boot camp, I've gotten to ride Feivel (16.2 hand chestnut oldenburg gelding), JD (16 hand pinto Irish Sporthorse gelding, also known as "the pony") and Taldi (big bay Irish Sporthorse gelding). Both JD and Taldi are Carlingford horses http://www.carlingfordhorses.com/, which I would guess are better known as jumping than dressage horses, but I could be wrong (remember than part about not really having the first clue about dressage - double for dressage outside of eventing).
So, I've gotten to do shoulder in (which I had done in the past), half pass at the trot and canter (new to me at the canter), serpentine with a counter canter loop (new to me though it does appear in dressage tests at intermediate eventing I think, or maybe 2*), 4 stride tempi changes (wow!!). And, it has all been hugely fun and has made me think much more precisely about where my aids go (although as far as I can tell, with all of these horses, you basically imagine what you want to have happen and it just magically occurs).
I am looking forward to getting Tag to some dressage shows as well as events this year and to the time when I get to do all these cool tricks on him.