Save yourself a ton of trouble and just use the Migration Assistant. It'll move everything from your old machine to your new one. No need to get your hands dirty with swapping drives.
+1
You do NOT want to use the OS from an older model. There's a good chance you'll end up with a big headache. Use the Migration Assistant. The only thing you might need to do afterwards, is to reenter a serial number or two. You will have all your apps, data, and settings. It should end up looking virtually identical to the MacBook you migrated from, except have the correct build of the OS for that model.
For instance: My old MBP (17" 2.33) was running the latest 10.5.6. I did boot off of it, knowing it would be different, but seeing a different display calibration (it was bluish), went off on a wild goose chase. Finally, I found that the new 17" UB MBP came with build 9G2141, whereas the old (public release) of 10.5.6 was build 9G55. One of the differences was a different "Color LCD" calibration - the other was a different Energy Saver pref pane, which was missing the GPU selection.
The "bluish" problem was exactly the same as many reported seeing on display models in Apple Stores. They ALSO used 9G55, instead of the shipping build. The problem arose because they have a standard network image for the store machines and hadn't updated the one used for the 17" UB MBPs.
Bottom line - IMO, trust the Migration Assistant. It does a very thorough job - anything missed will be minor, if anything.
for reference:
Mac OS X versions (builds) included with Intel-based Macs
edit: btw, the Migration Assistant is run automatically during the setup of the new machine