Unfortunately, or maybe 'fortunately', I never played the original SE4, so my experience thus far with Gold has been awesome!
I haven't tried TCP/IP with anyone yet, and to be honest, though I myself wouldn't mind getting a TCP/IP game going, its hard to find people to play TBS games this way.
But I can tell you that the extras included with on the CD is really nice! Not only are there mods and shipsets, there are also some really useful utilities and tutorials. The manual is well done, but veteran players might find it less than necessary.
Malfador and Shrapnel put the industry leaders to shame with this production!