I've been using Leaf for a while now it seems to work great. Only problem is there is little out there to support it, so using it can be a little difficult at first. I actually had to use the Hamachi wiki page to figure out some of the configs. The main reason I went to Leaf from Hamachi was hamachi was un-reliable. Some days I could connect right away and other days I couldn't get on at all. Leaf I have never had that issue. There are several other VPN clients out there but I'm running a Vista x64 machine and this is one of the only other VPN clients that would work other than Hamachi.
Machine specs:
AMD Phenom 9500; 6 GB DDR2, 650 GB HD; ATI HD3450 512MB; Vista x64