I was kinda in the same situation you are... I was into BMX in the early 80's, got out of bikes when I started driving, then drifted back to motocross and bicycles. I've had a couple of mountain bikes, a pre-WalMart Mongoose and later a Specialized Stumpjumper M2, but they were never really fun like the BMX bikes were.
My thousand dollar Stumpjumper still has the original tires on it 5 years later. Hah.
I just picked up a cruiser and for the size and style of bike I wanted, it feels pretty "right".
One thing that bugged me with the mountain bikes was the flimsy feel all the chain clanging over rough terrain, and the 24" single speed feels totally solid. I love that.
I started with about a $200 budget looking for used bikes on Craigslist (not much that wasn't junk), and quickly realized it wasn't going to happen and upped the budget. I then looked at the Haro X24 which was around $350, but didn't really do anything for me, though I can't say there was anything wrong with it either. It was just A Bike.
The bike I decided I wanted based on reading stuff on the 'net was the Intense Race Pro XL. I think that was in the $400 range, and still looks like a lot of bike for the money to me.
http://www.intensebmx.com/racebikes/IBK9MPCA-1.htmlThe Free Agent Ambush was my low dollar pick.
http://www.freeagentbmx.com/06-ambush_24-06.htmI shopped around local dealers about getting the Intense, but had no luck. The first guy I went to told me he didn't stock a lot of cruiser stuff but game me some brands which he could have next-day. One of them was SE. I was pretty blown away by that, just because of what SE was in the 80's.
I got some prices and told him I had to read up and would return. I looked at both the OM Flyer and the Floval Flyer and opted for the Floval. Basically doubled my original budget, but I really like the bike.
I gotta admit I'm used to the feel of a motocross bike and I feel very top heavy and far forward on a BMX or mountain bike, but I'm acclimating much better to the cruiser than I ever did to the mountain bikes I've had.