I went through the same thing several years ago when I first branched out from adventure as well. I really like the entire cyberpunk genre and I had heard good things about
Deus Ex, so I gave it a try and really liked it. I love sneaking and hacking.
Action-RPG hybrids can be fun if they're done well because they often have a fair amount of character interaction and sometimes puzzles, like adventures. Although combat can get intense and sometimes a bit stressfull (for me), it's worth it if it has a good story.
I'd like to go back to
Fallout 3 at some point (now that I know how to turn off the gore), but right now
Bioshock and
Mass Effect are keeping me busy. If you like futuristic settings, misslilo, you may want to have a look at those someday. The
Deus Ex series is great as well, if you don't mind going backwards in terms of graphics. Likewise
System Shock 2. They do have some fan-made "high-definition" texture packs which make them a lot more tolerable.
However, from what I've heard and seen,
Fallout 3 will keep you busy for a while.

"I have always felt that violence was the last refuge of the incompetent, and empty threats the last sanctuary of the terminally inept."
--The Marquis de Carabas in Neverwhere by Neil Gaiman