Jeff, the noise level and vibration is a big issue for me with window units. The friend I mentioned in my prior post had an old Frigidaire window unit mounted in the window directly above his bed. Without a headboard, the entire wall resonated behind the pillows.
In my own bedroom, the windows are not above the bed or even on the same wall, so I'm not as concerned about vibration as I am about the fan and compressor noise. The portable units do a much better job of quieting down their compressors, and that likely has a lot to do with their design. The "saddle" type units that Pete mentioned above are probably on par with portables for their noise level -- or even quieter, but like he said, they're not cheap either.
I should mention that I have central HVAC, but see no point in maintaining 67 degrees at night throughout the house. I cool the rest of the house down overnight with window fans, as nights tend to cool down nicely in this area during the summer months, and it's usually below 70 in all other parts of the house by morning.