Reporting back after nine months as a new Sky Club member, I have to say that was the best $350 I ever spent. Some things I have discovered:

1. Security at RDU can be randomly busy, but with the SC membership I don't feel like I have to time my airport arrival exactly. In fact, getting there early is a good thing -- time for a bagel and some coffee.
2. The occasional five-hour layover is no longer a problem. While it is still more efficient to be in my office, I can actually work from most of the Sky Clubs just fine.
3. The LAX-RDU direct flight is now my preferred method of getting home from the west coast. With SC access, I can play all day then shower at the LAX SC before the flight, so I don't lose a day. (I recently did this after a whole day at Laguna Beach -- that day pretty much justified the SC membership by itself.)
4. Notwithstanding the couple that decided to crack open their laptops in the quiet room at LAX last weekend, I usualy find the quiet areas to actually be quiet and suitable for a quick nap.

Yes, the SCs in ATL are horribly crowded, but this has been just another reason to switch to DTW, MSP, and CVG as my preferred hubs -- I've never had a problem at any of those clubs. Note, too, that I don't drink, so all of the above are independent of alcohol consumption. (If I drank, there would be no question whatsoever about their value.)

All in all, it was a good decision and I'll do it again, probably using miles: If I don't make DM next year, I'll cash in miles for three AMEX gift cards and put the SC membership on my AMEX CC for the points (thereby spending 33,000 for $300 GCs instead of 40,000 for a $300 SC membership).

Thanks to everyone who replied -- you have increased my 2011 travel pleasure by a couple of orders of magnitude.