The Mitsubishi Diamond Pro 900U sounds like a good choice, but you could probably do better for the money. I assume you're looking for a 19 inch model? If so I would say the Dell Trinitron UltraScan P991 is a good choice as well (Sony-made); they seem to be able to maintain a bright picture for a long time, but in my experience they are a bit more prone to burn-in than other models. The P991 can scan up to 107 KHz (good for 1600x1200 at 85 Hz) versus the Diamond Pro 900U's 95 KHz (1600x1200 at 75 Hz).
As neccrttv said, almost all CRT monitors made after the mid-90s allow you to adjust most of the geometry settings you'll need, such as pincushion, pincushion balance, tilt, trapezoid, parallelogram, and sometimes linearity, top/bottom hooks, and convergence. I wish more monitors had a bow adjustment, but either way you can still adjust the geometry to be pretty good. Earlier than that, multisync monitors were generally calibrated at factory for the preset modes and only have dials to adjust brightness, contrast, size, and position. The Samsung SlimFit TVs were known for geometric distortion because it's harder to control the electron beam once the neck is shortened.
If you have a desk that can handle the slightly larger size and a 60 to 70 pound load, go for a 21 inch CRT monitor. Generally manufacturers seemed to really focus these as flagship models, so they're all good. One of my favorites is the NEC MultiSync FE2111SB, which uses a flat Diamondtron aperture grille CRT and can scan to 115 KHz (I've run mine up to 2048x1536 at 72 Hz, and 1920x1440 at 75 Hz is no problem for this monitor). The FE2111SB also has 300 MHz video bandwidth (compared to the Mitsu 900U's 150 MHz); the higher the video bandwidth, the higher the resolution can be before the picture starts looking soft or blurry because of scanlines overlapping.
If you're really looking for something good, a Sony GDM-FW900 is an excellent choice. This is a 24 inch widescreen (16:10) CRT monitor that can do very high resolutions. However, these weigh close to 100 pounds and it's not uncommon to see them sell for several hundred dollars. Sun and HP also sold rebadged FW900s that are equally as capable but perhaps not as aesthetically pleasing to all. Oh, and if you can get a hold of one of the larger multisync monitors like the one neccrttv has, GO FOR IT, but these are relatively rare and will cost quite a bit more.
In short, these are all factors you want to consider:
- Maximum scan rate (resolution and refresh rate)
- Dot/stripe pitch (the smaller, the better)
- How the monitor is actually performing: color balance, black levels, strength of tube and phosphors
For that last one, consider using test patterns like Nokia Monitor Test and seeing how the particular monitor does with them. Brightness and contrast should be adjustable such that the picture is sufficiently bright enough for lighting conditions you plan on using it in while making sure that black looks purely black (and dark grays look a little brighter than black). When the picture suddenly goes from bright to dark or dark to bright, there should not be a major change in the size of the display area.