I just connect the new SSD using a cheap USB to SATA adapter, install Lion on the new drive, then boot from that new drive (hold the option key while booting to select an alternate boot source).
It asks if I want to migrate data from another drive, and I say yes and point it at the internal drive. Everything migrates over, you get to test things on the external drive to be sure all is good, then power off and make the exchange.
The benefit is this gets you a Lion recovery HD since some of the imaging tools don't yet perform that operation and only move the main partition data to the SSD.