Ah, another switcher-backer. Been there, done that and am very happy with SL. A word of caution, I don't think that Lion Mail works in SL Mail, not sure about Lion/SL Address Book and Lion/SL iCal. Just make sure you don't loose your old SL personal data.
I did a clean SL install then restored from Time Machine. It worked perfectly. The MP was only on Lion for a couple of days. Time Machine restored my last available SL backup just before I switched to Lion so I only lost a couple of days of email.