In all fairness, I don't personally think that there needs be more metamagic feats brought in. Using the APG and UM etc, there is already a huge amount of variety for spells. It feels a broader and more balanced than it did in 3e.
I have just finished a 6 month almost hyper accelerated game that went up to 10th level, and found that in all honesty the game dragged a little as more attacks were thrown in and such like. Part of that might be that the players were badly organised, but I also think that low level play is almost charming in its simplicity. I certainly know that my 3rd level ranger to some degree feels more powerful than some of the 10th level characters I saw because success is much more appreciated due to less skill ranks and such like. Success or failure on tasks gives a much more human element to the game.
My above comment will probably be disagreed with, but I have a pretty visual way of seeing the world, and whilst I optimize characters to be the best at what they do, I like to maintain a mortal element to it as well. I want the game to be a challenge at all levels, be it in or out of combat. When a character can succeed on a task on a roll of 2 or above then I begin to lose interest.