I am a .30 cal fan but I won't knock the effectiveness of the .270 family. I currently own a .300WSM, and, while it is a very good shooter I think I am closer in line to skydiver's way of thinking. The WSM's are fine but have trade offs as he mentioned.
One of the pros is that they don't have to be built on a long action. Some companies (I think Tikka) use the same action regardless of the case length so you don't save anything in weight for example. Availability of ammo, especially if you don't roll your own, is of critical importance to me.
I went to a gun show before Christmas and some guy had a closeout on factory ammo. He was selling stuff like .30-06 180grain accubond for $20 flat per box. The local shops all had it for around $43 a box before tax. I ended up taking the money I had brought for a new gun and bought 800 rounds of '06.
Now, due to my large stash of good ammo, I prefer my '06. If he had .300WSM, I would have probably gone that route or split it down the middle.
IMO If you have lots of other guns and want to try something new, go ahead. If you are a one or two gun guy, worried about ammo, etc. I'd probably stick with regular .270.