@ Those who feel 4E is a pain to track.
Does the group as a whole keep track of the game or do you expect the GM to do it all? While I do feel 4E has some hidden complexity due to how different one set of mechanics and one class can potentially be from another, I find keeping track of the action to be rather easy. In my regular group, everyone helps.
As a player, if I use a power which gives a boost, bonus, or penalty, I keep track of that. This might mean reminding the guy next to me what my power did when it's his turn. This might mean making a note on my character sheet which reminds me that I get a bonus to using a certain weapon because of a feat. I suppose I always assumed that writing things down on a character sheet was normal.
When I've GMed, I expect a little help from the players if they expect me to remember every fiddly bit about their character. Typically, I'm pretty good at remembering what's going on. As such, I'll try to remind someone if they forget something; if it's a new player, I try to cut them a little slack. However, if you suddenly remember that you should have done 5 extra damage a few rounds ago -sorry, it's too late. I'm not a jerk about it. I simply find that players get more in the habit of paying attention and keeping track of the game if they're expected to. The game is supposed to be a shared experience anyway.
Where I would say 4E has complexity is in what I briefly mentioned earlier in this post. It's possible to play one class and have absolutely no idea how another works. Likewise, it's actually possible to GM 4E without having any idea of how things work on the player side. While this is at times a good thing because it means you only need to know a little bit of how things work to be able to play, I think it can also cause complexity when a situation arises in which a judgement call is needed. I discovered this recently during my Wednesday game when one of the players decided to try an Essentials class. He was unsure how something worked; he asked me, but I had little to no idea.
This also bleeds into the fiddly bits of feats and powers and such. While I just said I find them easy to keep track of, that's assuming they're already on your character sheet. However, I think those things can be complex to understand because of the wide variety of how things can potentially work. I also feel 4E would greatly benefit from a rule which covers in what order exceptions apply. There have been times in which I've had a feat and a class feature conflict with each other over how they modified a power and/or ability. If there were a standard way in which exceptions took precedence, I believe that would clear up a lot of confusion about 4E. It's been a while since I've played Magic, but I remember there being a rule which details in what order different kinds of cards would apply. I believe having a D&D rule which might say powers trump the general rules, but feats trump powers (for an arbitrary example) would be a good thing.