I finally managed to finish it.
I confirm my first impression, for me this game was so boring.
It's all the same, you must do one thing again and again, and they put two identical levels (the boat ones) too.
It required me a month or so because every time I tried to play, I was bored after 15 minutes.

so it's pretty much like any other game in the franchise...

Yes, but I liked Legend and Anniversary, they have a decent plot and they weren't so boring.
Plus, one thing I really hated about Underworld...is the evil Lara.
You see her in cutscenes but you never fight her! What a joke :\

I also liked this game, and never had any of these problems, IIRC. Played some minutes of the Steam version I recently bought and everything was alright, too.

With that said, I do wonder if I'm the only one who liked TR Legend's combat system and Lara talking with her team, as there was none of that in the sequels. But still, out of this trilogy, I can't choose which game I like the most. Perhaps when I replay them all later.

I remember having some control issues with Underworld, and a bug in the final level, that i had to restart. I was hugely dissapointed with UW, since Anniversary and Legend [the only TR games i actually enjoyed] were so good. UW also had horrible performance issues on my rig back then, but that's a different case.

I remember I was so frustrated with some time puzzle to get some extra in the first Tomb Raider that I quit. I don't remember what the extra was but it definitely was not important at all to finishing the game.

Which one is Underworld? There are just so many TR games.

Underworld is the last released Crystal Dynamics main line Tomb Raider game. It goes along with Legend and Anniversary.

It's too bad they didn't get around to tying up that story arc. I hate it when plots get abandoned midway, which is why I prefer games that can stand on their own.