HL did not have a completely rewritten quake1 engine with realtime light/shadows like doom3, bumpmapping, reliefmapping and such great stuff. The DarkPlaces engine used in nexuiz is just BASED on the quake1 engine but its greatly improved and almost totally rewritten and is one of the most powerful and featurecomplete engines there is!

Actually there are only two q1/q3 alike maps in Nexuiz, all the other 20+ included maps are new to Nexuiz. Quite a few custom mappers were inspired by ut/q3 maps though.

Nexuiz uses a heavily modded quake1 engine, added effects like bumpmapping, reliefmapping, reflections, scriptable effects, realtime lights/shadows similar to the doom3 engine. Just downloading q3 sources? LOL you suck so bad at trolling.

Source is included in the zip file.. Stupid trolling on your part.

Well the next upcoming release should be a huge improvement for Nexuiz.. The renderer got a nice boost (in general +30-50%), the network code was enhanced to cope with high packetloss and high ping (ping 280, PL 20% was like ok), along with some other changes like a working wallhack prevention (well it was already there but was a high cpu burden on some map before and now its just fine) and ofcourse the usual big fixes, new content and stuff.. However you seem to be right about the problems with US players :)