VM performance greatly depends on the area. Where I live friends and family all had VM (slowest packs they offered) over the last 10 ish years and had great speeds etc while I was stuck just outside the city on a 1.5mbit adsl link. I've recently moved and went straight on VM's 100mb service. Love it. Had an issue with billing, but that was resolved with a credit to my account. Pretty much got the second month free.
Got 4 people in my house, 3 pc's 2 laptops 4 phones and a tablet, even the tv and bluray player connect. Often someone maxes out the link downloading demo's or updates. Had a mate round with his pc updating WoW, 8gb update, getting 12.2mb/s he sat there laughing.
Check the VM forums, search for the area you live. See what people are saying.
Personally, I recommend VM. My upgrade to 120mb is March, i'll see what happens to the service then.