One thing that crept into my game was analysis paralysis. My players got to late heroic tier and things began to shut down in combat. They had this huge pile of cards and all these options to go through, with magic items thrown in to boot. It became a little unmanageable.
My feeling with 4E was the cool bit about being able to do lots of different things, also became it's fault. I think level 3 is the golden level for 4E (possibly level 5). At that point players have 2-3 options of encounter powers and dailies, with a few choices of repeatable standard attacks (at-wills and basic attacks). As they level up, this just starts adding on. You get more and more options, and all those choices seem to gum up the thought process for players. They just have so many choices and feel that pressure of wanting to do the most optimal action possible during their turn. So I began to think about power expansion differently.
Instead of adding more and more, why not reach a set amount of powers and abilities and cap it? As players level up, instead of gaining more options they swap out powers and upgrade the ones they currently have. The emphasis of having more options begins to lean towards fine tuning and improving the powers and abilities they have. With that in mind, there are a few other things to tackle too.
One magic item with a power/tier - For my next game I am leaning more towards the magic items that give static bonuses, over an optional power. While it's cool to have that +1 acid sword that has a daily ranged attack, having another 3 items that also have daily/encounter powers just layers on the stuff players have to go through in their decision process. This can seriously add to analysis paralysis of the PC. If anything, I'll add more consumables and one-shot items. Dark Sun introduced the idea of static enhancement bonuses for players without using magic items, and that is something I am also seriously considering. Another option would be to bump up the items they have making that +1 dagger slowly morph into a +3 dagger with +2 fort vs. poison.
Cap the number of powers - Players will have a limited selection of standard powers as they progress. At most from the advancement table, they can have 1 At-Will, 2 Encounter, 2 Daily, and 1 Utility in-combat utility power. Players may gain additional utility powers as described, but their use must have some out of combat effect. This is highly subjective, with the final interpretation of a utility power being decided by the DM. All bonus powers from class or race are not subject to this limitation (ex. Channel Divinity, Wizard Cantrips, Elven Accuracy).
Last time I was talking about using a trained attack in place of your out-of-the-book basic attack as an option for players. At face value, it's really just a glorified at-will attack. Mechanically, it's no different from having a 2nd at-will power, but it's a subtle shift from an additional power to becoming a fall-back regular attack. Rather than having another card in front of the player, it's on the character sheet and emphasizes that point of when in doubt use this attack. It'll never be a horrible choice for a player to use the trained basic attack as it's geared towards their ability scores as an optimized attack.
Some classes are going to come out ahead with power choices. Your wizard and cleric are going to have more options than your fighter. But at the core of it, even the classes with limited choices should still have situational options. They just won't have a laundry list that's what is in the game now.
Allow for more retraining each level - At each level, players can retrain up to 3 powers. In addition they can retrain 1 feat. This is key to limiting powers. Each level you have to allow the player to get cooler toys. While they may not be able to add more to what they have, they can at least pick up powers and abilities to create interesting combinations and improve on the attacks they make.
Limited choices break down - This is far from perfect. Utility powers become a huge issue. Some classes get situational skill bonuses that transform into static bonuses. Some classes have utility powers that can only be used in combat. It's just the way to the cookie crumbles. By the book, at level 10 players have 3 utility powers tacked on to all the other powers they have. Utility powers make a good target for power pruning.
Psionic classes just don't work with this. This cap power limit is doable with your core classes, but psionic augmentation powers just break down. If anything, possibly the number of power points might be reduced. I don't play with psionics for my game, so not too worked up over this. Multiclassing and hybrid classes might need a little more tweaking too, however my players never really explored those options.
It's a huge game change, but I'm liking it. I think the focus shift from more powers to better powers will work out. It's far from perfect, utility powers especially, but having a cap on the powers players gain through advancement will likely allow them to have more focus, while still retaining a few options, and hopefully curb that analysis paralysis.