Right now, it seems like the rogues special ability is being "the guy who can succeed at non combat tasks more than 30% of the time", which is actually more of a reflection of how borked task resolution is for everyone who doesn't possess an expertise die, than any kind of special ability for the rogue.
To my mind, the rogue
a) should be as competent in head on combat, absent tricks, spells, etc, as the cleric. With skill tricks, sneak attacks, and so forth, they should be as good as a cleric who has a chance to buff himself with spells.
b) they should be able to do things with their skills above and beyond what other people can do, not just be the only people who can regularly achieve success with mundane actions (seriously, they need to make it so any class has a good chance to succeed with mundane actions). The fighter or wizard can ambush someone by ducking behind a corner, or hiding in the brush. The Rogue canhide from you in a torchlit room.
c) the rogue shouldn't need a battle buddy to shine in damage. Nothing about rogue screams "team player", but since 3rd edition, to do their schtick, they need to basically stick like glue to some other person in order to get the requisite flanking. Please, oh please, let them actually be awesome on their own, not just as part of a fighter-rogue "package".
Oh, and if you want to throw in the ability to trigger wands and scrolls at high levels, that wouldn't go amiss either.
