I've been using the v7 Beta for a long time now and I like the new features. Most of it is what I would consider fluff, whistles and bells, though. For your absolute basic needs of just sending IM's to other people, Windows Messenger is probably still your best bet.
Messenger.MSN.com
The final release contains a number of improvements over the beta. My favorite of which, is the slightly more compact design of the main messenger form. My contact list fits into a slightly smaller space now. The mainform also shows a very scaled down version of the user's picture, rather than the generic red, green, and yellow icons, when available. There are also some new winks included (small Flash animations that you can send to other IM users), and the handwriting feature is always fun (be sure to install Journal Viewer to use this feature).
The coolest fluff feature, though, is the new "personal message". You have the choice of typing a personal message, just below your name at the top of the main form, or you can use the "What I'm Listening To" feature. This feature will load song information from WIndows Media player, and let anyone who has you as a contact, see what you are currently listening to.
There also appears to be some integration with the MSN Spaces service, although I've been unable to get this to work yet (I have problems with passport on my machine, which prevents me from automatically logging in). I'll try to get this working some other time.