Aaaah RahXephon. Like so many, after being blown away by the awesomeness of Eva who went looking for similar anime, Rah was first on the list. And thus we realize that we don't REALLY always want what we wish for.
Viewed outside of (and some time away from) the spectre of Evangelion, it's a pretty damn good Brave Raideen remake.
Viewed right after Evangelion, it's a shameless and piss poor knockoff with better art direction and sound, but piss poor characters, storyline and mecha/kaiju.
I was brutally disappointed after first viewing, especially the ending which was a more shameless then the rest of the series knockoff of EoE. However watching it again years later, I am able to enjoy it on it's own merits quite a lot better. While Ayato is the most boring, juiceless protagagonist in all anime, some of the supporting characters, the ones who aren't giggling smug snakes or direct clones of Eva cast, come off fairly interesting. The story is also far better the 2nd time around, though it suffers from some terrible pacing flaws and the ending is still a shameless EoE knockoff no matter what.
The music is absolutely the best thing about this series, especially the title song. Easily up there with GITS:SAC, Noir and other legendary themes.
So yeah, worth watching, but NOT if you've recently discovered and fallen in love with Evangelion. :)
"Yes ladies and gentlemen, in France Asuka swears like a sailor and confirms that she's the butch of her apparent lesbian relationship with Mari, Mari insults people that ignore her, and Shinji Ikari tells to Sakura Suzuhara and Misato Katsuragi to go fuck themselves!" -ElMariachi