You know you're a masochist when instead of using Migration Assistant or just starting again, you go through every folder you can think of that was changed (not necessarily directly by you) in the course of owning your computer.
I've just finished migrating to my new MacBook Air (new for me) from my Pro. I had a lot of files, such as certain preferences, etc. that were important to me, but wouldn't have been migrated with Migration Assistant. I also didn't just want to clone the HD, since
- The MBA SSD capacity is smaller than the MBP capacity and I needed more space. I managed to solve this by not transferring my whole iTunes library, which was 110 GB, mostly podcasts, followed by a few movies and TV shows.
- I didn't want to transfer a MBP-specific installation of OS X onto a MBA. This would probably just have caused problems in the future.
I didn't migrate perfectly. There were a few things I forgot, but not much and they weren't very important (just the position of Dashboard widgets, as well as the notes that were saved in the Stickies widget, plus some other stuff). All in all though, I'm enjoying the speed of the SSD and the light-weight. Plus, the higher resolution display is awesome for fitting more apps in my menu bar.
One tip for migrating without Migration Assistant is to not. Try a Dropbox 100 GB account.
For people who like to mess with system files or install command line apps like me, learn from my mistake. Make a note of any changes you make/apps you install, or install something which does that for you automatically. You'll need that list when you upgrade to a new computer and you want to start without moving all your cruft across, but also need important files in hidden folders. For example, I installed a bunch of command line apps in the '/usr/local/bin' directory. When it came time to migrate my stuff, I just copied them over to my new computer. This means I miss the man pages and documentation for them. Easier just to list them all, then reinstall the first chance you get, that way you'll get the binaries, plus the other stuff that comes with them.