I play Xerath :s
Damn good at it too. I've beaten "hard counters" like Ahri, Kass, Karth, Ziggs, and Cass who either can take advantage of my rooting for easy skill shots (Karth and Cass), are highly mobile (Ahri and Kass), or have comparable range (Ziggs). You just have to get used to the mana usage. He's not mana heavy like Anivia, but he has to spell spam, so he can run out of mana if you aren't careful. He's also incredibly reliant on positioning. But by late game, he's one of the special few AP carries that stays viable in terms of damage because of dat % spell pen. Easy 80% pen with masteries and items. You can also afford to run ap yellows on him with less risk because of dat_passive. I'm pretty sure he can start with 30-40 ap with no items at level 1 and still not be a complete glass cannon.
Needless to say, I love to play him. Plus I have the molten Xerath skin, so ima pew pew alldayerrday.