If you are a new user, I would go ahead and upgrade to Lion before you get used to SL. That's what I did, and I love it! I had only used SL like 2 weeks before Lion was released and I hadn't done a lot of customization because I knew Lion was coming out. Plus, I wanted to be sure that I got it while the upgrade was free!
If you've only had the computer for a short amount of time, the changes of having apps that aren't compatible is pretty low. I had none that were incompatible. I absolutely LOVE the new gestures that were introduced in Lion! I thought I loved them in SL, but Lion is ever better. I also really like Launchpad and Mission Control.
I am always an early adopter, but I never notice the bugs people complain about. Most people hated Vista, I never had a problem. Upgraded to 7 the day it came out, though, and it was like night and day. Also got the iPhone 4 the day it came out and never had any of the problems that people complained about. Of course, YMMV. You've got the discs that came with the computer so if you upgrade and absolutely hate it you can always re-install SL. Oh, and for your slow download problem, either get Apple to install it for you or go somewhere with a fast internet connection and download it yourself. Took me like 30 minutes on lunch break the day it came out at a local coffee shop. Good luck, and I think you'll love Lion and not look back!