Zuiko lenses in general (at least the ones I've used) are pretty excellent. I looked around at the two 135mm primes (the f/3.5 and the f/2.8) for a while, and while the 3.5 was cheaper, they were both very reasonably priced. Right now it looks like you can get a very clean copy of the 3.5 for around $80, while the 2.8 will run about $175 to $200.
