Yeaa.. GENERALS is very poorly coded Net-wise.. I mean.. I can be playing Warcraft3: Frozen Throne with nasty lag or an iffy connection and yet it still plays fine with 2 other colleagues. LAN plays MUCH faster but how often can one "gather the troops" to play at one location whereas Internet is more practical?
Sincerely doubt anything will change with the impending ZeroHour addon but one can only hope.
Remember though: Generals' SAGE engine and latency preformance depends on what the slowest machine is being used on the connection, what kind of map (is it an urban map with lots of things going on), and, if using my advanced AI Skirmish scripts, how complex the AI routines are?