Synergy seems to be working fine, but when I switch to the client pc in
the game, and then try to look around, it spins either looking up or
looking down. Can't get it to look horizontal. Basically, can't use
mouse look correctly. Any ideas?
had the same issues with synergy when i was using it around 1-2 months ago. Ended up forking out $20 and paying for similar software called Multiplicity
http://www.stardock.com/products/multiplicity/

works a treat, currently have it running on my main (Vista Ultimate 64bit) and running on my laptop (Win XP Pro 32bit) dont have any issues with mouse look etc, that i was getting with synergy and it also broadcasts the keyboard. (Dont think u can tell it to only broadcast certain keys tho) But with Hotkeynet, its not needed anyway.

If ur willing to try an alternative (even tho it is not free) there is a trial version available