I think playing as a Big Daddy will be quite fun. He is the prototype after all, so he's not brainwashed.
Plus true Dual-Wielding a Plasmid and Weapon at once, high-level Plasmids actually mean something other than more power, and of course Plasmid Combos!
Cyclone Trap can be combined with Electro-Bolt or Incinerate! for an elemental trap that does electrical/fire damage plus the fall damage. If it can be combined with Winter Blast then it may well become an instant kill in rooms with high-ceilings and a high-level cyclone trap.
And it looks to me that the weapon-variety is nice too. And some weapons are multi-purpose. The Rivet Gun is a rapid-fire weapon with 3 distinctive ammo types, and I THINK is the equivalent of the Pistol in Bioshock 1.
And weapon upgrades look to be nice too, like new drill-bits for the Bouncer Drill.
Also...
Spoiler:You ALMOST played as a Big Daddy in the final levels of Bioshock 1, and the ALMOST was lame in my opinion.
*edit*
Also, Splinter Cell: Conviction coming on February 23rd for 360 and PC. It's going to be awesome.
[Edited by Foxxie-kun, 1/6/2010 1:29:19 PM]