I am always amazed by what the hybrid community cooks up. We usually do not mention Hybrid OS releases but Cole let us know about a BlackBerry Storm2 9550 hybrid that is making its rounds that is getting rave reviews. It was created by the team at BBHybrids.net and reports so far are that the hybrid is super fast/snappy and leaves you with 148mb of free space along with a ton of other improvements.
Keep in mind that hybrids are Frankenstein-like OS builds where hardcore BlackBerry hackers mash together files from multiple different OS versions to make a better OS release.
HUGE WARNING: Hybrid builds are not meant for the faint at heart. They are not even beta builds and you will get ZERO support from RIM in getting them to work. On the other hand you can get some serious performance gains by using one so this might be worth a shot if you know what you are doing.