I felt the same way when I purchased my Macbook Pro (2006). Since that day however I have felt a higher level of purchase satisfaction with this computer than any other product, from my truck to my toothbrush, I own.
I used to be a chronic computer desktop upgrader, never going for more than 4-5 months without getting the new latest and greatest whatever.
The purchase of the mac was a landmark for me personally, suddenly something I cannot easily upgrade? O M G !
The result: 2 years of perfect satisfaction. I like it so much that even the new line that was just released isn't that tempting, while I WANT to upgrade, I don't HAVE to upgrade. I know that many "normal" people keep computers for 3-4 years or more before upgrading, but I have never understood that, I spend far too much of my life on these things to allow myself to become that outdated.
Then I changed (read: grew up and became a Mac user at the same time). These two things are mutually exclusive, but the purchase itself was timed perfectly and I am still more than pleased with my laptop (although I wish now that I had a 15.4" of the exact same specs because I travel more now and the 17" is a bit too large for in-flight usage).
If you are worried now, just wait till it shows up. I am sort of jealous that this new release is getting the new laptops to people in a matter of days, when I bought mine it was a 3-4 week wait for them to show up, 3-4 weeks of the deepest pits of hell.
I hope you love it!