You'll never find a Bowflex for cheap. I haven't worked out in a while, but IIRC, the cheapest model would be the Bowflex Sport, and that's $800 before shipping and whatnot. Similar machines, like Weider, will prolly run you around $500 or so... if you're just into getting shape and not really building muscle, then these machines will suffice.
Like someone else mentioned, Bowflex doesn't use real weight conversion. 10 lbs. on Bowflex is less than 10 lbs. of free weight, but the upside is that the risk of injury is greatly lower since you're using a cable system.
Which reminds me, Bowflex is only versatile because you have to keep switching and hooking up cables to hit different muscle groups. This gets annoying fast, and there are models where no cable switching is required, but they're also a lot more expensive.
I read the article Scorch posted and what surprised me was that the XTLU was one of the defective units, since that's the top-of-the-line model. I was always skeptic about the lateral tower, but that still wouldn't stop me from buying the machine.
Overall, it's a great machine, but if you really want to improve muscle definition, you should get some free weights to supplement it.