Mac Mini 2011 migration to new iMac 27"?

I have a MacMini 2011 dual core 2.5GHz i5, 8GB, Radeon 6630M and a 750 GB internal hard drive running Mountain Lion 10.8.2

I am going to get a new 27" iMac when they appear December 2012 (or whenever).

I plan to use Migration Assistant (Setup Assistant?) to move my Apps and files and settings etc over to the iMac, unless there is a better (safer?) way...

1. What should I watch out for when doing this? Any "gotchas" or things to worry about?

Both Macs have Thunderbolt ports. The Mini has FW800 and the iMac has USB 3 (but no Firewire).

2. I assume its best to do the transfer via Thunderbolt? Anything to watch out for here?

The Thunderbolt-to-Thunderbolt cables are VERY expensive. What alternatives do I have? I can set the Migration up and let it run all night, so speed is not really a huge issue, I think. (The Mac Mini main hard disk has about 90 GB of system files and apps and things on it. Most of my huge data & video is on external drives, so not a problem)

Thanks!