I just bought one of the last special edition box-sets to be found anywhere, and I must say that I am pleasantly surprised at how FUN this series is. The animation and voice acting (original Japanese) are good, if that's a concern of yours. You will be disappointed though, if you're looking for a morbid, serious and highly melodramatic story line like 'Evangelion for example. Nurse Nanako specializes in providing plenty of fan service, and laughs (read my 'sig for example). Don't let the DVD tag lines fool you however, as there is virtually no nudity or any sexual situations, something I had a problem with I might add.
Think of this series and this type of anime as an alternative to more serious anime titles that usually involve a young, sulking Japanese boy who doesn't know anything, doesn't come from a good family and is caught in a struggle for the end of the country/world/universe/human existence, etc. Actually, I can't think of many anime titles that don't involve that particular formula...
When watching this series just try to have a good time. Damn it, where's Area Seven when I need him....