Iron Sky
Procedurally Generated
I'll have to take a look at how 4e runs in high levels--I've never played or run anything in 4e, and I honestly don't know how to get started.
We've found that the speed of combat, at least, seems to mostly increase with the amount of status effects being thrown around. I've developed a pretty decent system for tracking them on my laptop as I run combats, so it doesn't take too much time.
There's also a wide variance depending on how long your players take on their turns. Our players vary anywhere from taking about 15 seconds on an average turn to a minute or three.
As to where to get started, I'd say get the PHB and look online for Raiders of Oakhurst (an EN-made adventure), whip up some characters and give it a go. I was pretty sold just by running test combats with stuff put together by ENWorlders before the game came out.