I just got my first one a few days ago, but wasn't as disappointed (maybe because I didn't have a vintage one to compare it to). It's a fairly "vintage-style" circuit (kind of primitive, low parts count), and from researching the subject on the Internet, it seems that only a few components have changed through the years-- mainly, they don't use the LM308(?) op-amp because it's now rare and expensive (tho available at
http://www.smallbearelec.com/home.html), a few resistor values may be different, and the Turbo Rat uses Germanium diodes... but it's still basically the same thing (I think).
The build quality isn't too bad-- the switch is kinda funky with its bare input and output leads though. My main complaint was that it was impossible to get the knobs off without destroying the pots-- they were on split shaft pots, but very, very tight.
I was looking for a box that had more extremes than a Tubescreamer-style overdrive, and the Rat 2 has that. It can do an articulate OD at the barely-on end of the gain pot. At the other extreme is a super flubby fuzz. In between you can get some really harsh and loud lead tones. Basically though, it's unruly: I wasn't fond of the fact that the controls seemed to interact with each other (changing gain and volume changed the tone) so it took a lot of tweaking to dial in a sound. On the other hand, changing the guitar's output volume has a big impact on the distortion level ("cleaned up nicely").
I think the state of distortion effects has come a long way since that circuit was designed...
-Jim
