I use Dragoons early on, and have toyed with Reg. of Cav. but haven't been very impressed. The larger unit size for Dragoons helps their survivability and improves the odds for breaking morale.

I agree that cav in ETW is less powerful than in previous TW games, and that doesn't really bother me. Heavy Cav was the powerhouse in nearly all earlier games (except maybe RTW), but I feel that Line of Foot really shine in ETW and I think that's rightly so.

I use cav primarily to mob up routers at the end of a battle. I also put them on the flanks and use them to more quickly encircle the enemy forces as Line Infantry are kinda slow and clumbsy when you ask them to change their facing too drastically. I usually end up having Line Infantry forming a big C around the enemy and then charging my cav in from the open portion of the C, into the rear of the enemy line. I'm happy that the battle AI seems to do a good job of keeping my Line Infantry from firing when friendly units are too much in the firing arc, so I can charge into this shooting gallery pretty safely.

I haven't had access to any lance-based cavalry in my GB or Prussian campaigns. I tried Malta and Papal States once and I think they get them. I think France might too, so I'll have to give that a shot. The lance-based forces have much better melee and charge values at the cost of defense, but since we seem to still want to use cavalry primarily for a charge that breaks units, my guess is that the lance-based cav units in ETW would do a better job. I'll have to try and see if that's true.