I use a ULS model M-300, which is a 50W CO2 laser head. I use an air assist on the cutting head, at about 50 psi, which helps cool the cut point and keep the flammable vapors down. I also run the laser at 1000 dpi, which gives me a finer cut.
A laser cut will always have a slight kerf on it, meaning that things like cubes/boxes (for things like lens alignment) will need hand finishing. Of course, the thinner the part, the less of a problem this is. For most items, this isn't a problem, and you can usually compensate somewhat by over/undersizing the cut parts. It took me a lot of wasted parts to start judging the "error" in measurements to induce.
If you really have serious bubbling issues with the laser, I suggest reducing the power output and upping the cutting speed. Then just overlay multiple passes, which will give the part time to cool between hits. I find this works REALLY well on softer plastics (like ABS) but delrin might benefit, too, especially thicker parts. As I mentioned above, that air assist nozzle is, for me, a must have.
I made a dive reel by stacking laser cut rings on a core (laminated a stack), and in the last dozen or so dives, I've had no problems with it holding up in some pretty rough Pacific NW waters at fairly chilly temps.