Speed issues concern me a lot too... heover I have a Pentium III so I'll wait for the result of the beta tests to know if MP slows down your computer.... normally, with scripting disabled, the new version of Messenger Plus! should even be a little faster. Enabling scripting won't slow down the system by itself, however, your scripts might so be careful
By the way, I've added a page on my web site so that you can be aware of the progresses in the developement of MP2.... if you're interested...
http://www.patchou.com/msgplus/mp2.htm