I had a rev A MBA bought when it first came out. It didn't do much for me. It couldn't perform my basic Mac needs.
When the rev B MBA came out (was finally shipping), I had just bought a unibody MB and it took a lot of convincing to buy the rev B after my original experience.
I made the switch to the rev B MBA and could NOT be any happier. The rev B is a perfectly capable Mac even as a primary computer. I use mine as my primary computer. I have the 1.86 GHz and the SSD... however, I have tried the 1.6 and HDD.
Remember that the new 1.6 GHz with HDD is faster and a better performer on nearly all levels than the original MBA with 1.8 GHz and SSD.
The best of the MBA is available to all. A wonderful Penryn 45 nm CPU with 6 MB L2 Cache. Nvidia graphics with Mini Display Port that can drive up to a 30" Apple Cinema Display. I played HD video on my MBA to a friend's 30" ACD and it was stunning. Looked just like the Mac Pro was driving it. The low end has the same 1066 MHz DDR3 RAM at 2 GB which is plenty for most. The low end model only has 8 GB of less space. Both have same great form factor, same great display, and same lightweight portability.
I would encourage you to buy the rev B MBA any day of the week. Mine is lightning fast because of the SSD. It actually blows away both my unibody MB 2.4 and my MBP 2.33 GHz, both with 7200rpm HDDs, and both with 4 GB RAM. BUT, the low end model is plenty powerful. Keep in mind that the majority of the differences are when opening applications and large files, and when booting up.
To the other poster, it is true the MBA is in mid product cycle, but it could be a long wait for a rev C MBA. The 1.8" drive in 256 GB is hard to come by, as I have been trying to find one. The SL9600 Intel Core 2 Duo was slated to be released next month, but information has been scarce and is reporting only a 2 GHz clock speed, which is hardly worth the boost. In addition, Adamo was released and at its thickest point, the Adamo is thinner than MBA... I HOPE Apple keeps the same form factor for the MBA in rev C, but I fear Apple will go crazy trying to win the thin war, even though it already has won the thin war... and won the style war.
I think the wait may not be worth it if it ends up being a long time... and especially at the lower end model. The rev B is SO GOOD at so many things, that the rev C cannot improve nearly as well as the rev B did from the rev A.
Best wishes with your rev B MBA...