For everyone who has had issues with lag please give the Networking beta a try.
(@Squidgy, @Heureka, @Miige, not you @nevir, @Combatman12, @Scortion, @sikerow, @dwarvenname, @Nyuudles, @ranox410, @Jenndragonfly)
The details for accessing the Networking beta are at the bottom of the Release 147 announcement (Steam Beta unlock password is SXG7buBiOohbTjQr3nz6).
If you can report the result it has on your networking + lag experience then we can consider making it an official release.
Thanks!