I have recently started using proxies for my SEO research and for creating a more natural backlink profile. I use a combination of my own EU proxies and proxies from http://www.sharedproxies.com (great service btw) and I have found that my teir 1 links seem to be performing better then before when most of the links were coming from a more limited range of IP addresses. I have to do some more testing but when I checked my site today I was amazed at how many more indexed backlinks I had then just a week ago when I was doing everything from my own IP address.