IMO, a 2.3 GHz processor is more practical as a real minimum that should be able to run the game, and a 2.2 would be pushing things:
Wrong.
I want to put an end to the GHZ myth that's taken as the truth in this thread.
1: Not all GHZ are the same, please remember this. A modern 2GHZ i3, for example, will dominate an older 2.5ghz core 2 duo.
2: The graphics card is the main bottleneck. If you have a laptop, this means your CPU probably isn't the bottleneck.
3. Oddly enough, Skyrim seems to be a well threaded game. While the majority of games are generally limited to 1 or 2 cores, Skyrim seems to take advantage of quad core CPUs. This means those seemingly slow i7 CPUs in 15" and 17" macbook pros are actually very fast.
Personal testament to this: I Have an AMD A8-3500M CPU at 1.5ghz in a $579 HP Dv6 laptop. Yes, 1.5ghz. And this is a slow 1.5ghz, since the old K10 CPU architecture has a low IPC. So you can think of my processor as a 1.45ghz Core 2 CPU, or a 1.2GHZ i3/i5. BUT My processor is a quad core, so it can spread the load out to multiple cores. Still, my processor is very crappy compared to a modern laptop i3 at 2.0ghz+
I also have no dedicated graphics card, or dedicated video memory. Integrated graphics: bad news for Skyrim right? Wrong, this isn't Intel. The A8 has 6620G graphics, meaning it has powerful integrated graphics that can use the laptop's normal RAM. I can play Skyrim on high settings with a few mods with no problem, despite my crappy CPU at 1.5ghz, all BECAUSE I have a decent graphics card.
Just for a test, I overclocked the processor to 2.05 GHZ, just to see how it would affect gameplay. Indeed, my game was a bit smoother, but not by much.
The moral of this story: Don't obsess over CPU speed. See what graphics card your computer has, go to notebookcheck.com, and look it up to see what it's capable of.