I just used my power roller for the first time last weekend. It worked great - cut the painting time more than in half. A couple words of advice, however: First, make sure you also get the paint pad attachment, as the roller assembly will not permit painting next to trim on the left side. Also, make sure when the instructions tell you to tighten the roller with a screwdriver, you do so. Otherwise, it will work loose and the paint will drip out the end.
There are a million gazillion little parts in the unit that have to be cleaned when you're finished, but overall, it's worth it, especially if you hate painting as much as I do.