I do not recommend the whole Unreal Gold. Just Unreal released in 1998. Return to Na Pali is one of the biggest craps I've ever played. Unreal (1998) is really well-made game in classic FPS style. Gameplay is addictive, weapons are diversified and every player will be satisfied. There's also some nice maps but in fact I can find few levels (Chizra - The Water God Temple, Bluff Eversmoking...) which I really hate. Unfortunately, I saw some AI bugs but it's some kind of Unreal's appeal. I confess I was not interested in the storyline (I know just the overall meaning) so I won't tell you anything about it. Last levels are really great for me - short, "quick" and good. ;) I played it on 'unreal' difficulty level (the hardest) and I finished the game in more or less 20 hours (I have started it twice).
I have to say something about Return to Na Pali... It is really bad. I thought it will be as good as Quake's mission packs...but no. Levels are boring. I was waiting for the ending during the whole time. I met AI bugs in every level. What about new (3) weapons? Hm... I was using just two of them Combat Assault Rifle (yeah, it is one of my favorite) and Grenade Launcher which I don't like. The third - Rocket Launcher is just weak and useless.
I finished this erm... mission pack in 8 hours. And if you really want to try it I will just tell you that I prefer to abacinate myself rather than play this again.
Unreal Gold is worth buying. But you should try just the main Unreal game.