Much of what 5.5e changes (as of the most recent playtest doc) is stuff I don't really feel fixes any of the issues, it just shuffles them around.
A few of the changes are really quite good, but rarely go far enough (e.g. the Playtest 7 Warlock gets...1/day half their spell slots back. Woop-de-friggin-do. But it also makes pacts into invocations, which is great.)
Most of the changes I actively disliked have been rescinded, which means I'm not really against 5.5e, I just have few reasons to be for it.
Overall, I think it will be better; I just struggle to summon enthusiasm for 5.5e because of how dim my view of 5.0 is. To put it into perspective: If treatment A cures 5% of people who take it and does nothing for the other 95%, and treatment B cures 50% of the people who take it and does nothing for the other 50%, then treatment B is clearly superior to treatment A, but it's still not an adequate response and we should work to do better.