[sisforsurfing]

There are lots of really good M42-mount lenses. You can also use Leica-R, Nikon-mount Zeiss (though at those prices I'd go for Sony's Zeiss stuff) and Nikon-mount Voigtlander.

The main annoyances;
- your camera might not meter. I'm not sure about Sonys. The lower-end Nikons dont but the higher-end ones do.
- as you stop down the lens, it actually stops down, rather than using auto-aperture like you're used to. It's like holding the DoF preview button down the whole time, only you can't not. The solution is to focus wide open, then stop down, meter, and shoot. That sounds like a bigger deal than it is.

I have an Olympus 100/2 that I use this way.

If you want to try it out get a $7 adapter on eBay and some fun, cheap, reputable M42 glass. There's plenty of info all over the internet. Something like the Jupiter-9 85/2 or something even cheaper.