One of the primary things I am looking forwards to in 5e is faster combat. I LOVE 4e combat (and fully intend to bring elements of it into 5e, the base combat seeming a little bland for my tastes), but with both my groups heading towards the pinnacle of their stories, the battles are getting more massive, more complex - and, if I do say so myself - more awesome. However, the speed at which these battles happen is slowing right down.
This is, I think a combination of things, including the wider variety of powers available to the players, and the larger numbers of enemies they tend to face. Also, despite my player's character's have massive damage output, but the hit point total of the mundane monsters outpaces even their inflated (by base 4e's standards) killing ability. This doesn't bother me when we have boss / demi-boss (solo and elite) fights, as they are supposed to be long, painful affairs. However, when fighting the rank and file servants of these monsters, I don't really want a battle lasting three sessions (as the latest Ormid et al battle has).
So, what to do?
I don't want to continue to inflate player damage output, as that can get way out of hand, and present massive problems further down the line. Instead, I intend to halve the hit point total of "mundane" enemies, with a few tougher guys getting their full allocation (including all solos and elites). I'm hoping that this will allow the massive battles that are going to occur to unfold, without us getting bogged down in long, boring battles that loose their fun factor.
Also, as we don't use XP, there is no game impact beyond quicker fights!
I also use the amazing 4e Combat Manager, which lets you adjust monster starting hpts with a single click. This is fabulous!