MiniMatt

If that's the crack I think it is (the half open connections one) then I'd seriously advise against it to be honest.

Two reasons, first, allowing more half open connections won't increase your speed or the number of peers your connected to, what it will do is increase the speed at which new peers are contacted, ie. it'll ring up more at the same time - the same number of peers will still come back saying "yep, I've got something" or "no I've nothing for you" or just not respond at all. Data isn't transferred across a half open connection, it's merely initial handshaking. Ergo all that happens is that with the patch you can "ring up" peers at a quicker rate, it won't have any impact on the number which answer and want to talk to you.
Second reason is that tcpip.sys is forever getting patched, sometimes for good sometimes for bad, but I'll give Micro$haft the benefit of the doubt and say overall their patching efforts are for the best. Unless you're manually hacking the file then all your doing is replacing your "up to date" stack with a version that was created (last I looked) several years ago.

That said, the reason Msoft gave for the half open connections limit was bizarre at best (something about slowing worm propogation if I remember correct - all it would do is knock tenths of a second off a worm contacting X number of potential new victims).