I've used the 2011 MBA 13" Ultimate for almost 5mths solid as my primary machine.
it's benefits: ultra light portability, decent cpu power (excitedly unexpected), and the 1440x900 resolution.
I recently switched to the 13" MBP - and UNLESS these features come down to a MBA type body it'll STILL survive even with lacklustre internal resolution:
2.8Ghz Core i7 Dual-Core CPU: Hyper up to 3.6Ghz!! (it starts where MBA tops)
Expandable RAM: 16GB is supported! (So Pro: Audio/Visual Pro apps)
Reasonable price on expandable HDD! ($450-700CAN for 450-500GB SSD SATA3) - MBA: internal SSDs capable of moving data at up to 200MB/s only)
Higher external resolution
Faster Thunderbolt port (full 10Gb/s Quad channel; Air has only dual channel 10Gb/s); I won't see this using the low end LaCie TB HD but on a TB-RAID setup I would.
pricing for SSD ugprade, and ability to upgrade RAM alone made this a no brainer at $50 before taxes (CAN) and I get a 750GB 5200RPM HDD to begin with. (BTW, that hard drive blows chunks; with SSD the MBA only has resolution beating the MBP).
I currently have the base model early 2011 13" MBP w/ 120GB SSD. And I really do like it, but I also have it sold. Transfer of ownership by August. They are buying it with the original HDD for $1050, warranty through March 2014. I can obtain too much money from my current rig it seems silly not to upgrade one more time before being content for the next 2-4 years.
This is the reason I'm looking, and the reason this topic interests me.
With that being said, if I still get the same feature set of the MBP 13" as the 2011 models (disk upgradeability, running SSD+HDD, memory upgradeability), then I will probably get the 2012 model and load it up with my current SSD+HDD and 8GB of memory.
Toying with my wife's 13" MBA a little this weekend, I'll take the Pro every time. But then, I reviewed the 11" MBA again. If it had a little more power/battery, and an option for more memory I'll have a hard time talking myself out of it.
For work I might be at 6-15 different locations in a typical week. This is where the 11" has it's appeal.
So right now it's down to an 11" MBA (with 6-8GB of memory) or the new 13" Pro (assuming there is one).
My main grip with the MBA 11" was the battery life and the low resolution. They really need to work on those two elements for 2012.
From my reading on the matter I think with Ivy Bridge the CPU will be about 20% more efficient in power usage. That is why I anticipate about 6 hours of battery for the 11" MBA and 8.5+ for the 13" MBA, and the Pro models.
That leaves screen. For me a 13" MBP screen is already a concession. Almost every work day I'm connected to servers and user workstations, some of them running dual 1080p monitors. I realized the 11" isn't much worse, and I intend to plop a 22" or larger monitor at the key offices where I frequently find myself. Thus the appeal of the 11" MBA. For digging through code and scripts, etc. I've come from the X series of Thinkpads. I'm used to working on that kind of stuff on a 12" screen for the past decade. A 2 1/4lb with that much power is hard to ignore.
We'll see. I'm afraid I will have to until at least June before the models I'm interested in will be available.