I pre-ordered one as soon as it was announced even before seeing it in person. I did get to spend some time using the Air at Macworld and it is an amazing machine. It's not for everyone, but it exactly what I've been wanting in a laptop: VERY Portable and Thin, light, yet a totally solid build, great screen, great battery life, runs cool and silently, yet is quite fast/responsive. I don't really use a CD/DVD drive on my existing laptop (USB flash drives and ripping/re-encoding DVD's to mpeg4/DiVX for on the road viewing works great, just takes some advanced planning). I don't plan to do any video on this laptop (I have a desktop for that, which actually has a slower CPU than the Air as it's older) and I already have everything wirelessly networked for file transfers, video/music streaming and printing, etc.
Some have panned the Air on the fact that there is no built in 3G/WiMax for cellular/wireless communications. Not a deal breaker for me as 3G/WiMax is not universally accessible nor a solidified standard here in the US and some areas have better coverage by one company than another. The addition of a wireless 3G/WiMax modem means more bulk/power use/expense to squeeze into any laptop. Given that there is not one dominant standard in all areas of coverage, why force someone buying the Air into one solution? I suppose you could always use one of those bulky/ugly EVDO/3G USB external adapters (already supported in OS X BTW), but remember, the Air has Bluetooth 2.1 + EDR. I can easily tether the Air off my current 3G cell phone via Bluetooth and access my cell provider's network that way. I'm already paying for one cell with a data plan, why not use it instead of having to pay for a second cellular data plan (which are NOT cheap BTW).
The non-replaceable battery is not a huge big deal for me as Portability/size was key for me and a design allowing for a removable battery would require a thicker/bulkier shape. It's an acceptable trade off especially if you consider how easy it would be to make an external battery pack that would feed power via the Magsafe adapter for long trips (and if it was built with multiple tips/cords, it could also maybe feed/re-charge other devices like your iPod/iPhone, Cell phone, GPS, etc). It sounds like the internal battery isn't that difficult to replace every few years as the battery wears down (as all rechargeable batteries eventually do).
If you're looking for a tablet form factor, check out this authorized Apple Macbook modification:
http://www.axiotron.com/index.php?id=modbook
I got a chance to use the Modbook as well. While it's quite full featured, it's also MUCH bulkier and heavier (and more expensive to boot). As good as the ink input is, it just isn't that easy/seamless to use for heavy text input without an external keyboard. It would suit someone who's primary software tools work well with a pen/point and click interface (drawing/graphics/photoshop). If you're looking mainly for a web browser, e-mail and e-book reader, it's probably an overkill.
I think the mousepad gestures in the Air really makes a leap in usability that I'm sure will trickle down to all of Apple's laptop (ie. alot less mousing around and having to click on all the little buttons, or constant mode changes between typing and mousing).
In short, the hardware and design is amazing. It's priced well for an ultraportable laptop IMHO (accepting that you'll always pay a premium for more portability, can't get around it) if you don't want an "everything but the kitchen sink" type laptop. My current 15" Titanium Powerbook has essentially become a desktop that stays at home as it's just a bit too big/bulky/heavy and fragile (believe me the Air feels more solid/sturdy than even a current Aluminum Powerbook or a Macbook, no flex or creaking at all) to want to tote along everywhere.
I can't wait to get it in early February, I'll be sure to post a more thorough review when it does get here.
Dave