Mass Effect 2: What We Know So Far

OXM took a moment to summarize the information that's been made available about the plot, combat tweaks, new abilities, and uncharted worlds in BioWare's Mass Effect sequel.
This has received lots of tweaks since Mass Effect, mostly in the form of regenerating health (no more medi-gel) and thermal clips (serving as universal ammo for all weapons). Weapons no longer overheat and there will be no grenades this time round, probably a good thing as they didn't really work too well in the original. Sub-machine guns, heavy pistol are machine pistol are a few of the new weapons.

You no longer need to spend level up points on your weapon class either, as you will be fully effective in that weapon if your class supports it. You can now target individual parts of the body and you have to manual enter cover rather than automatically, a la the original Mass Effect.

...

On the biotic side, new abilities include Pull, Shockwave, Charge and Slam. The new tech abilities include Combat Drone, Cryo Blast, Incinerate and Tech Armor.