I bought 3 used Dell P991 (rebadged 19 inch Trinitron) monitors on eBay in the past (one for myself, two for my dad's video editing computer). One was fine, the other's blacks weren't quite right, and the third one had this awful red hue (some calibration was off and the only way to fix it would be to pay a technician to open it up and recalibrate it's internal, non-user accessible controls).
Overall, I'm happy because my purchase price was low, but if I had to do it again, I would only purchased an used CRT monitor that I can personally physically and visually inspect (i.e. Craigslist.org for your town) or get it from somewhere that has recalibrated it to original spec (I think there was an ebayer named cosmicdallsd or something that does that).
Otherwise, I would just buy an LCD (lower power consumption may save you some money long term).
EDIT: the Dell P991 Sony Trinitron rebadge does have a potentially beautiful picture, but remember that CRTs degrade with age, and unless it is packaged correctly, it will be damaged in transit (e.g. the plastic base of one of mine was cracked).