Not really. I mean yes, they have the same spellcasting system, unlike in 3e where bards, sorcerers, warlocks, and wizards all had different styles of casting, but in terms of just about everything else - no, not really. From my experience in 4e wizards and warlocks feel very different, with wizards hitting lots of people with little bits of damage or putting them to sleep while warlocks pretty much flay one or two guys alive.
Actually, the party in the campaign I'm running has both a warlock and a wizard and the way their style comes across is quite different. True, some of its just flavoring. But mechanically, they're pretty different as well.
Now, having not run a sorcerer character I can't confirm or deny how different the sorcerer's going to be. But I imagine it'll be about as different from the wizard as the warlock is, though it might be a little too similar to the warlock. Hopefully, though, the warlock and sorcerer will be as different as the rogue and ranger, which have worked out pretty well in my mind, possibly through the controllery-aspects of the class as well as the "everything and the sink gets hit" flavor to many of the powers.