Considering adding a lift - thoughts on 2-post vs. 4-post?

How much do you know about the foundation you're putting the lift on?
If it wasn't poured with a lift in mind, it may not be appropriate for a 2 post lift.

(and, if you go 4 post, get a sliding jack - or two - that makes tires/suspension work easier - and pay to have them delivered/installed - they're friggin' heavy! ;-) If you're not familiar with them - you can see some here: http://www.gregsmithequipment.com/4-Post-Lift-Accessory/Rolling-SLASH-Sliding-Jacks)