I find it amusing that in System Shock 2 there are what, six French-Epstein devices in the whole game. In Bioshock 2, they're dime a dozen, and you can shoot them out of a gun.
I do like the new hacking system, even if it is painfully easy to hack a bot while it's attacking you.
The weapons seem strange to me. A lot of them are basically reskins of the previous guns, with minor differences (mostly in ammo types). The biggest differences are in ammo types and magazine sizes, but for the most part they're analogous.
Don't take the above as ohmygodtheyruinedit criticism, just idle observations. I'm finding Bioshock 2 to be an enjoyable game. Not exactly groundbreaking, but most of the changes from BS1 are welcome, the plot seems interesting enough so far (I'm at the art place), and it's still a good shooter.
One thing that really irks me, though- Why oh why did they use a health system that forces you to mash heal every few seconds in combat? Why give you a short health bar and five medkits when you could just have a health bar five times bigger and have medkits be instant use? SS2 had an inventory, so it made more sense, but in Bioshock and Bioshock 2 it's just an instant use health regeneration.
If you choose to sit in a chemical storeroom in SS2 waiting for research to complete then that's your choice. The MFD tells you exactly what chemicals you need so a quick pass by the storeroom to grab it/them is the only detour required before returning to your mission objectives.