I got the Bowflex SelectTechs on a sale. The max is 55lbs. I think they're bulky for some exercises but if you have a larger frame you might get used to it quicker. Other than that, it's very easy and quick to change weights. Cons are its bulkiness and that it's usually a 100 or 150 bucks more than Powerblocks. Don't have experience with Powerblocks.
http://www.walmart.com/catalog/product.do?product_id=12080237&findingMethod=rr I got some of these, but I got them cheaper than listed at Walmart on sale a long time ago. Forgot how much though.
I have some Ironmaster adjustable dumbbells. Have used both powerblocks and the bowflex ones, but think Ironmaster feels more like a regular dumbbell.
When it comes down to adjustable DBs it usually comes down to Powerblocks vs. Ironmaster. I have Ironmaster because they were a little cheaper, are more like a traditional DB, and fit my needs. Powerblocks will change faster and work well if you're into supersets and the like. Try craigslist. I found a set of Powerblocks for ridiculously cheap. I woulda bought them over Ironmaster but someone beat me to it. Still I am very happy with the Ironmaster DBs.
