The only time I've heard fan noise on my new 13" MB Air (i7 CPU, 4 GB RAM, 256 SSD) was after I had migrated 216 GB of files from my 2010 MB Air. I chedked using Activity Monitor, and the CPU usage was almost entirely due to Spotlight indexing. Haven't heard any fan noise since, and the Air stays barely warm.
Tomorrow FedEx will deliver my new Pegasus Thunderbolt RAID system, and I'll offload quite a few GBs of data from the Air to it. The only gripe I had with the 2010 MB Air was slow I/O via USB 2.0. Thunderbolt will make the Air a real (and fast) workhourse for my document databases -- and I'll have a lot more room for databases that I couldn't cram onto the 256 SSD in the 2010 MB Air.
The light weight of the Air is important to me, especially for travel. I've got bigger Macs with more RAM and quad-core CPU, but I found myself choosing to work on the 2010 MB Air most of the time.
The only unfulfilled wish connected with the new 2011v Air is that it doesn't have more than 4 GB RAM. I try to avoid hammering away at the SSD with Virtual Memory swap files, and have worked out some tricks that let me almost totally avoid doing that.