Don't worry about those people who say to return it. May I say, Congratulations! You bought a great machine that will hopefully last a long time. I am using a 20in aluminum iMac with 1gb ram and 2.0ghz processor. It was the first gen, and frankly, while it is a performer, the earlier produced ones were not ready. I had mine replaced. Yours should be fine considering it is a revision. Don't worry about an upgrade. At the very most, your included specs could be a 2.6ghz processor, 2gb ram, and a 320gb hdd.
Also, you may want to look into a backup solution. You can use Time Machine and an external drive for that. Just go and get a garden variety external HDD about twice the size of your internal drive (possibly 750gb-1tb), open up Disk Utility, and format it for HFS+, tell Time Machine to use it, and a few hours later, you should have your first backup.