Yep personally I would say the only one you might have to worry about is the Cleric, which is in fact a mildly overpowered class.
Shifter as Ruleslawayer said could be problematic, but is not neccesarilly unbalanced.
Psionics, to me (not mental powers but "psionics" as D&D has them) dont fit well into regular fantasy, but I dont think any of it is going to hurt balance.
The swashbuckler is a fine class, although it does get more in some ways than the Fighter, but thats a problem with the Fighter. I dont remember all the details of the Dervish but it seemed fine to me as well when I looked at it.
In my game (if it survives any further due to scheduling issues that is) I am allowing the various basic planetouched (genasai, aasimar, tieflings) without even having the level adjustment since to me they arent drastically stronger than a 3.5 gnome or dwarf
I see no reason why people cannot stick to core. Their is no reason to be Genasi this or half-whatits that.
Ummm....except that they want to be? That they want some variety? That it fits the type of character that they want to play? That they are tired of elves and humans and dwarves?
I see no reason why some people insist on sticking to "core". The idea of "core" is nice for d20 publishers to have something to base things on, and it works as a deccent common ground for discussing balance (since trying to discuss all the possible variables of balance if this or that other thing is included would just be impossible) but for me in terms of actual play, there is no "core".
And as someone has already mentioned...in the Forgotten Realms setting, Genasai, Drow, Aaismar, Tieflings and Deep Gnomes are in fact "core".