Honestly, what I would do is buy the base i7 model with the base memory and hdd space. That way, you can upgrade the regular hdd on your own to a 7200rpm drive...which will mean you now have 2 drive instead of one(upgrading it from Apple). Then, if you want, you can upgrade to a ssd in the future, and have other drives to use as backups.
If you have the means, get the best processor your wallet can handle. Do worry about the ram, 4gb's is more than fine for the average user. There actually is a great difference between the 2.3ghz-i5 and the 2.7-i7. At idle, the i7 already beats it. With the i7's turbo-boost mode at 3.4ghz, it's a no brainer that it will handle just about everything faster.
There are also other reasons to consider the i7: It comes with 4mb L3 cache instead of the 3mb of the i5. The hdd already comes stock at 500gb, as opposed to the 320gb of the i5.
I have a feeling that if you didn't know much about the ssd, you can do without it until the prices come down a way bit.
The MacBook Air, while a very nice computer, is also limiting in terms of changing the hdd, and ram. Although people do use it as their sole computer, it's not really meant to be the sole computer for all daily use.
I would either go for an i7, or wait until the back to school program starts. That way, you can recoup some of your money back.