I was a little frustrated when I lightly skimmed the sorcerer class. I mostly play Warlock right now, and the thing that marked a warlock in 3.5 is "blast! Blast! BLAST!!!" without letting up, light ranged damage *forever*, as opposed to large damage, a limited number of times per day. In 4.0, since everyone can blast blast blast forever, the warlock has been distinguished by being a skirmishing striker--they're strongest when they're mobile, moving from target to target. They become harder to hit when they're mobile, if they're closest to the target they get a +1, and the more targets they face, the more people they can tag with their +1d6 Curse and the more times they can draw their bonus powers as the other PCs wipe out their previous targets. So, they're highly mobile, sneaky blasters with some control powers.
Sorcerers are ALSO strikers. But they're not sneaky at all. There are two flavors--Chaos Sorcerers (which are really a bone to the strange players, though they're a neat class), and dragon-blood sorcerers, a bit more heavy damage-dealers. Both flavors seem to have a lot of ways to blast people close to them, a range of near, mid, far, attacks. Both have a few different methods of shoving people who get to close violently away, which is neat.
Tanking: At least in the first PHB, there were three hit point tiers--wizards (10 hp + con + 5/level or something), warriors (15 hp + con + 8/lvl or something), and everything else (12 hp + 6/lvl, I think). Sorcerers are in the "everything else" catagory, able to take a few full-on hits before falling over. In addition, both have bonuses to spell damage based on STR or DEX, and at least one flavor has a bonus to AC from a casting stat. So, there's a fair bit of encouragement for them to wade into combat--they're not that bad at it.
In addition, their focuses are daggers and staffs, both legitimate close-up weapons. Not like friggin' orbs and wands.
So, in summary, sorcerer wading into battle, dagger flashing, blasting everyone within three squares with gouts of liquid fire, well-toned and leather armor. I'm okay with this image.