I use MSN Hotmail and Messenger, among various other programs for instant messaging, and to be fair it is quite good. Your contact list is updated to show whether any friends are online, and when you are busy there are various status icons you can use to make sure you are not disturbed. And there are the usual block user etc options too.
The actual email program is fairly good too. Any incoming emails give you an alert via the messenger if you are online, which can be useful if you are expecting a message but dont want to keep refreshing the hotmail window. Their server is quite fast (considering the amount of traffic it must have), however their service is not without its faults.
Spam constantly arrives at the hotmail account, however a few precautions should stamp at least some of it out... blocking senders of spam, reporting all spam via spamcop.net or another similar service, not replying to the spam / clicking anything in it......
The mailbox is quite small too, and I am constantly being told my account is nearly full, which is a bit of a pain, but thats just life I suppose!
You get what you pay for with most things in life... at hotmail/msn you pay nothing, and you do get a fairly good service.