According to PELIT magazine, Bioshock doesn't have an inventory system, so basic tools (first aid kits, hacking tools, plasmids, ammo and weapons) aside, you can't store stuff for later use. The author also said the game appeared very linear, as in there wasn't a lot to explore, but that could have just been tactical guidance in the beginning. The new EGM says there's a journal, map and a "mission arrow" (WHY) which suggests a more sprawling level design though. There are also different difficulty levels and harvesting Adam shockingly occurs off-screen.
Are weapon upgrades in? With no inventory they are probably weapon specific which is rather disappointing.