Every time I get on a plane I wish I had an Air, but it's just not justifiable. Not only do I have and use my 8GB RAM (Photoshop, Parallels, browsers, Rails + large test suite), but the peripheral ports are critical. I don't think my Time Machine backup would ever get off the ground without the initial Ethernet plugin, not to mention the times when the DSL goes out at the office I can just plug into the hardline normally reserved for our Mac Pros. Also Firewire is another thing that may not be needed every day, but hurts bad when you don't have it (need to transfer a couple GBs between Macs quickly? Compare to wifi to Firewire Target Disk Mode). Even the SD card reader is quite handy. I'll leave the optical drive out because honestly that would be fine as a peripheral (although I do salivate at the thought of a top-tier 64GB SSD boot drive + 1TB data drive in optical drive bay).
I do have a bit of Air envy from time to time, but then I count my blessings that I live in a time where I have a portable workstation that I can use as my primary machine and carry from home to work every day. That is amazing in and of itself.
Lack of peripheral options has stood between me and an Air as well. Fortunately, once Apple releases a Thunderbolt version, this will quite soundly turn the issue on its head.
"(although I do salivate at the thought of a top-tier 64GB SSD boot drive + 1TB data drive in optical drive bay)."
SSDs are interesting in that they get faster as they grow in size. top-tier 64GB SSD drives are quite a bit slower (at least in write speeds) than their 128GB counterparts, which are slower than their 256GB counterparts. Write speeds scale almost linearly with size.
It's more correct to say that their speed scales with the number of flash chips. The larger drives are faster because more of the controller's channels are populated. A larger drive that has fewer flash chips because it uses a new fabrication process can be slower than a smaller drive built using previous-generation chips.
When I bought my 160GB Intel X25, my understanding at the time was that the fastest SSD available was a more expensive 64GB drive. I haven't looked at the landscape for a while now though.
I do have a bit of Air envy from time to time, but then I count my blessings that I live in a time where I have a portable workstation that I can use as my primary machine and carry from home to work every day. That is amazing in and of itself.