I have three level 60s and bought two things that won't decrease in value anytime soon.
Soon is very relative. Every day more and more "keep worthy" items are being found not to mention the easier loot tables in 1.03 and lower difficulty Inf A2+ means more loot to saturate the market.
Ultimately though, in retrospect, it's not that different from what happened with Diablo II and D2JSP, which one could argue that it (D2JSP) was just an unofficial "auction house" of sort.
The most significant difference being is the people making the game are not profiting from the sales. In D2 they could focus on balance and adding cool features to the game. Now (I fear) more development cycles will be spent on ensuring additional layers of security/auditing as they are now accountable for that real money they are processing. Not to mention the temptation to make some choice loot modifications to help bump up AH activity.
When I first heard about the GAH I was very interested, made it safe and easy to get some value out of that super cool item that wasnt of any use to you. The 15% fee was a gold sink that only affected the users using that feature rather than say jacking repair costs that hurt everyone. The RMAH however I was far less enthused about, but ultimately time = money, spend 10 hours grinding for XXXX or spend an hours worth of your salary and get it now. I do believe the current prices are super inflated, likely people are seeing some activity on $20-$200 and they figure they better pay up and buy some l33t gear and grind out more items to recoup their investment. Likely it will work for some people, but I have a feeling that window of big ticket purchases being somewhat limited.