No there is no backlit on the 2.0 model. And they should be plenty available by that time period. As far as the performance, I went with the 2.4, but because of three things:
a. I almost always go for the higher end machine if I can. I got a 2.8Ghz 24" iMac when the Aluminum came out August 07.
b. I wanted the backlit keyboard, but even though the $300 was not necessarily a good price per performance increase, the keyboard, speed boost, and extra drive space made it acceptable to me.
c. I will be keeping this machine for some time and figured all of the the above items keep it more current than the 2.0, especially with HDD space, and resale value.
But no, there won't that much a performance difference, depending on what you use it for. At $1,299 US or less for a refurb, the low end is a good buy for a really nice looking and feeling machine. If you are on a budget I would recommend going with that model, that is without knowing more of your general use and needs.