Basically, I’m looking to do more work with free weights, but I don’t always feel like hitting the weights when I’m at the gym (which, I’ll be honest, I don’t go to enough anyway). These dumbbells look like a good way to get a range of weight (for doing things ranging from, say, curls to deadlifts) without cluttering my apartment up, and that’s cool. Also, I’ll admit that I like the gadgety aspect of them. 
I’m wondering, however, how long they’ll hold up over time (or, I suppose, if they just suck, right out of the box.) So…any experiences, opinions?
They’re a bit noisy.
I can’t recall what particular brand I’d tried once, but the plates also jiggled around on the bar just enough to cause a minor change of balance.
Didn’t buy 'em, so no idea what the durabiity is like.
I got my Bowflex SelectTech 552 dumbbells a little over a year ago along with the stand and bench, and they fit very nicely in my little studio apartment. They’ll do anything regular dumbbells and a bench will do, and still look almost brand new after all of the abuse I put them through.
I had a set of PowerBlocks for a while and they seemed to be a pretty good quality product. They’re not especially loud, and they are pretty easy to switch weight.
However, if you’re one to drop your dumbells when you’re done, I could see them getting damaged in short order. Each weight plate consists of two vertical plates connected by long rods. The plates nest together, depending where you put the pins will determine how many of the plates get lifted. The individual plates are not terribly sturdy looking, I’m sure they’re stronger than they look, but I still wouldn’t go banging them around.
Since you have to return the weight to the “nest” when you’re done, you have to be careful about it because it’s a tight fit. I don’t know much about the long term durability, I only had them for about a year before giving them to my dad.