I tried it out, without any major problems.
I'm a little worried about a couple of the services on the list it suggested closing, but it don't know for sure. I did find this site that gives more info on all the services though, if anyone it interested: http://www.theeldergeek.com/services_guide.htm
When it brought up the list of applications to close, it did list my AV and my firewall... though none of the apps were selected by default - so i don't recommend blindly selecting everything at this point.
Strangely, it DIDN'T select some of my other tray apps, like ad-aware.
Saved 88mb for me, though i'll have to wait and see if it really makes any difference.
More research needed...