My Bionic has been getting relentlessly slower too, to the point that it's really getting aggravating. My wife's iPhone seems as speedy as the day she got it, FWIW.
I did a full reset after the Jelly Bean update and it seemed to be reasonably snappy after that. Now its just seems mired in digital sludge when trying to do anything. I regularly kill open apps (ZD App Killer, though most, zombie like, quickly rise from the dead), and that gives some mild, temporary benefit.
Is this just some inexorable thing we need to get used to, so many apps, services and whatnot getting jammed on our phones that even with speedy new processors, they soon get overwhelmed and bogged down? Is there some way to more effectively manage what services, accesses and whatnot are going on (beyond basic settings and, say, ZD App Killer)? Or am I missing something basic I need to be aware of/doing (school me here then)?