Well so far I've only seen Yoda/Grevious, and Han Solo/Fett.
All of the above are basically combat monsters, except Han, who's more like a glorified combat medic. Actually Fett reminds me a lot of the Jet Trooper in SWBF1 before he was nerfed by the Patch, plus a flame thrower.
In all, I think the Heroes are pretty well done, considering. They have a few more saber animations so it doesn't look quite so boring (most of them seem automatic, you don't have much control over what swing you use), and they die quickly if you don't know what you're doing.
For example I became Yoda, encountered Grevious, and killed him in about 3 seconds. You have a block button but I think most people forget to use it and I have no idea the limitations of your blocking. But it doesn't seem like you can really "duel" it's just whoever attacks first/fastest.
The Heroes have their time based bar, and hitting them enough defeats them (your character just crouches in defeat and you get sent back to the respawn screen).
I think at least the non-Jedi heroes can still use vehicles (which could come in handy) and can capture control points (out of vehicle of course). As a reward for a killing spree it's not too bad. Ditto for unlocking the last two classes (you get the first four automatically, the rest have to be earned via points, though I'm not sure if it's your team's points or just you individually... ie: does every player have to unlock them for themselves?).
Unless of course this changes in the final version... but so far in the Beta it's kinda fun.
Too bad they couldn't have done something similar for the (otherwise horrendous) Space map...
(like unlock a better ship or something)