I was thinking closely about this subject: splicers in Bioshock 2. In the first Bioshock, there were a total of 5 splicers, including Thuggish, Leadhead, Nitro, Spider, and Houdini splicers. So far, trailers have shown only one new type of splicer: the Brute. My concern is that the game will lack more variety between these types and/or the game will lack different and new types of splicers (excluding brutes). I'm also concerned about the difficulty of conflict between splicers and Delta. Delta is a Big Daddy with powerful weapons and even the use of plasmids. This makes it look like Delta could be undefeatable against such weak enemies like Thuggish splicers. My guess is that 2K intends to make these fights drawn out and BIG. What I mean is they might have scripted the game to locate an entire group in certain spots to fight Delta. This would make it much more challenging when dealing with the game even in the easiest difficulty. I just hope 2K uses splicers to their full advantage. On an unrelated note, I hope 2K made some interesting boss battles. I was slightly bored by the fight with Dr. Steinman but Cohen and Wilkins were fun for a while.
2K Marin ended up removing the Nitros from BioShock 2 in favor of Leadheads that simply randomly throw grenades at you, keeping the splicer variety at 5. Also, the Alpha series, which your Big Daddy is a part of, has less armor than a standard Big Daddy in favor of speed, so you take just as much damage from splicer attacks as in the first. I was kind of disappointed that Marin didn't try making the game a bit more different from the first, because really, the enemies are basically the same, only less variety and more big boss battles with brutes, Big Sisters, Alpha Series, etc.