Another one to research: The Bosch ROS20VSK. I had the older model and recently got the newer one. I too like the Porter Cable, but it's about twice the price of this one.
Things I like about the Bosch:
Small and light --> no fatigue on large pieces, which I've had with other models.
Excellent dust containment. The cartridge filter is 'pretty good'. But if you hook it up to a shop vac, the dc is excellent. Unlike prev versions, the new model comes with an adapter to fit a standard vac hose.
Quiet. I can finally sand in my basement with the kids asleep upstairs...
(minor nice touch): The case has guideposts that you slide a sanding disc onto and then press the sander down onto to make the hole alignment perfect.
I got mine reconditioned from CPO Bosch. Good experience.