Hamachi is pretty good in my experience, though I'd never use it for DP (whats the point? just setting up normal port forwards is a much better permanent fix to any connectivity problems you might have).
I use it for games like C&C Generals, GTA2, etc... which are older and can have real problems in playing over the internet without it.
You can have some problems with it on certain ISP's, at least in the UK. When I was on PlusNet, it seemed their traffic classification system held up encrypted UDP packets (such as those used in the default hamachi VPN's) as a matter of policy; this meant really high latency and dropped packets - problem was solved when you configured the tunnels to be unencrypted, however this is obviously less safe.
- Dagless