The changes since RC1 are only engine side:
- new command: cd loop name, plays cdtracks/name.ogg as if it were a CD track (useful to mappers). Analogously defined: cd play name. That way, a mapper can bundle his own audio track to a map without having to fear track number clashes.
- command history in the console behaves (entering an empty line no longer empties the history, cursor is correctly positioned at the end of the selected history line just like in bash)
- curl status text changed from "(will connect 1.2.3.4 when done)" to "(will join 1.2.3.4 when done)" to be grammatically correct
- new cvar: con_term_colors ansi, outputs the server console in ANSI colors instead of Quake color codes; con_term_colors strip, removes Quake color codes from the server console (this feature might be subject to change for the final version)
Oh, and here something about the new jumppad property "height" which might be of interest to mappers: the height value works like described in http://t.div0.ccc-offenbach.org/jumppads.pdf - jump pad tuning should be much easier with this.
As for installing the patch - "extracting over" should be the way to go if you are on Windows or Linux, and on OS X the preferred way is to copy or move Nexuiz 2.0's data...pk3 file into the extracted patch. You can also extract this over the RC1 patch without any problems, however, you could then delete RC1's datapatch20060810.pk3 to save some hard drive space.