Now that you've had time to digest my thoughts on the narrative and gameplay of BioShock 2, please indulge my thoroughness. I have a lot to say about specific aspects and systems of the game as well, particularly in comparison to the original.
The gameplay-halting tile-swapping minigame used for hacking technology is supplanted by a realtime needle-stopping diversion that I feel is a better fit. It keeps the excitement high, and provides some options when it may be better to avoid an alarm entirely, or when the free first aid kit might be worth the risk of a more difficult needle stop. Also, the ability to hack remotely is a godsend. (I can't tell you how much EVE I used in the original to stun turrets with Electro Bolt or distract them with Decoy.)
Speaking of Plasmids, only one major new addition was included: Scout, a sort of astral projection plasmid for looking ahead. (Remind anyone else of the Gamecube game Geist?) Enrage and Hypnotize Big Daddy were consolidated into one, and the elemental powers have all been elaborated and differentiated at different levels of advancement. (Oh, there is another new Plasmid, but I really shouldn't mention it.)
Weapons likewise stuck pretty close to what worked in the original, and improved everything else. (Thankfully, the Chemical Thrower was thrown out.) Rivet Gun : Revolver :: Drill : Wrench. Rocket Spears, Phosphorous Buck, Solid Slug, and Trap Rivets all stand out as brilliant additions. The Drill and its limited supply of fuel make for a well balanced weapon; the Drill may be fucking nasty, but you can't just Drill Dash through every obstacle.
Like the less obtrusive hacking, the Research Camera is reinvented in a video format, awarding more research points for film of the subject assaulted in creative, non-repetitive ways. It flows much better with the action, methinks. But for God's sake, don't forget to research the Big Sister every chance you get. You'll thank me.
Enemies are expanded very nicely. Nitro Splcers were combined into Leadheads, which makes for a tougher foe, and a more treacherous force when combined with Thuggish hordes. Massive gorilla-like Brute Splicers, primitive Alpha Series Daddies, the new Rumbler Big Daddy, and, of course, the sleek and deadly Big Sister round out the competition. It doesn't take too long to learn the different tactics these types employ, but once you've got a Brute and an Alpha closing in while a couple of Houdinis flit about, the battle gets pretty fucking frenetic.
I've but dabbled yet into the prequel Multiplayer. I played a few rounds of Survival of the Fittest (aka Deathmatch) and found the action to be frantic and jarring. Part of this, of course, is my unfamiliarity with the levels, as well as my character's lowly status. I did win my first match earlier today, thanks in no small part to grabbing the Big Daddy Suit twice. Gameplay in the single player mode stops while you open the weapon or plasmid selection wheels, so engaging in combat in realtime suffers from a bit of a disconnect. I'm going to keep on this mode for awhile, though; I'd really like to see how the Multiplayer-exclusive Aero Dash and Houdini Plasmid play.
I'm on my second playthrough now, rescuing Little Sisters this time instead of harvesting them. My conservative habits that left me extremely wealthy and well supplied by the conclusion of runthrough one have kept me in luxurious comfort so far. I've only had to buy the odd EVE Hypo here and there to keep moving. I have an urge to focus on the Plasmids I neglected last time, like Winter Blast, but with the lower ADAM expected, I can't be too liberal with my purchases. Decoy and Scout are likely to be my first purchased plasmids now that I'm in Siren's Alley. I'm focusing on the Rivet Gun and Shotgun as far as upgrades, as they each provide a chance for EVE-free elemental damage with their final improvement. I've also got Keen Observer equipped, so that I can knock out all of my research ASAP.
Well, that's about it. I'm sure I'll have some more tidbits from the second playthrough, and I'll share my thoughts on the complete Multiplayer package once I've levelled up a bit more and have tried all the modes. In the meantime, if you're playing this great game feel free to drop me a line, you know, in case you're stuck, or just want some splicing advice.
Remember, "A Man Chooses."