we use access-it and to be honest it's been great. support is top notch, have given me guides and help at very short notice, the librarian loves it too
We went through this pain with .NET when we upgraded, we held off for a year as they were having so much bother at schools who had adopted early, and were advised to by the SLS
Main Issues we had were:
Slow to access resources (latest updated fixed this) (December 2009 ish)
MLS Scripting Internet Explorer Plugin causing the keyboard to drop characters
very limited documentation.
Email setup isnt detailed in the older manual versions and the details of what .NET needs is buried in the .NET directory on the server.
Identikit doesnt really work.
Various UI bug's (guarding salutations only displaying 1st character from manual import, Silverlight doesnt resize properly on a 15" screen)
it does have nice features and can help bring a library to the pupils but there are too many rough edges and i feel the customer is doing alot of their testing.
They have been trying to sell us the hosted solution and the moodle plugin's but we are not going to be doing this as we have just got it to a stage where it is nice and stable and working well, also their support desk can be hard to get hold of, however when they supply the information it is clear and easy to digest.