I'd buy. Or wait. No, buy! Yep, buy (probably)!
I've had two rev A Airs, I purchased both as refurbished. I never before or since bought refurbished and I can tell you that with the second one I was very disappointed. The hinges were loose and there was a high pitch hissing noise coming from the left hand side of the grill. But for these incidents, the 14 day return policy might be useful. Overheating is usual with Apple portables, so either ones were an exception. Yet, typing on it was a joy, compared to my 2.4 GHz unibody MacBook. But video - as you said - is something that these laptops should not be mixed with.
A friend of mine has got the follow-up and it is so much better. 1.8 GHz would be the minimum for these that I would take again. SSD is good, but not essential. Personally, I would recommend buying a refurbished rev B model. It is a good compromise between portability and usability. We can expect serious improvement only on the power side and usability. It just cannot get much lighter or smaller.
If you think about what sort of changes Apple might introduce, it is not difficult to see that their options are limited. Probably the new Airs will have a glass trackpad. 13.3" is a very practical size, the screen will probably get an upgrade. Processor speed might jump up to 2.26 GHz. Memory will hopefully increase - and hopefully it will be upgradeable (at present it's not). New battery will come too. The shape itself is getting dated. I expect some minor cosmetic improvement. Mini DisplayPort might come and an SD card reader. The price will remain the same, I think. The dilemma will be that there are so many similar computers in Apple's line that the Air will have to be specialised. If it will come out with the Tablet, then a SIM card or some 3G compatibility might give it the edge it needs. But this speculation might be childish to some. We'll see in the spring, perhaps.
So, it will be a nice little machine, IF(!!!) Apple puts the necessary development and testing into the project. First versions tend to have quality issues, so you might want to wait for the fourth rev, anyway. Let somebody else pay for the prototype testing.
TO SUMMARISE IT:
If you really need an Air and the 13.3" MB Pro is not light enough (although they are definitely faster), buy an Air now. I wasn't sure myself so I bought the cheaper, 2.26 GHz MB Pro and either I will get some cheap RAM and HDD upgrade or will sell it as it is when ones with matte screen come out. If you don't mind the screen, then get the 2.53 GHz version and you will keep it for several years, I promise. Don't wait for months with such little certainty about the new Air's specification! If you want the Air, the refurbished MB Airs maintain their value well, so computing will not be a major cost if you consider that you might want to keep it for at least 8-9 months if not longer. I mean, the Air is losing the reasons to buy it, but it would be stupid to downgrade it within the range; so this will be a tricky upgrade for that product. Almost anything can happen, so limited are the possibilities.
I hope it helps, sorry for the wordcount, I'm a bit tired. I hope I haven't confused you more.