Well, let's start with the positives. Black Mesa reimagines Half-Life's famous military complex in a very beautiful way - it almost looks like a real place. Shooting is fun - fighting in general is very enjoyable and guns behave as you'd expect - and new soundtrack is awesome, though not as good as the original. Some of the added things and NPC's bring much needed life to the place, and the game looks as good as you can do with original Source engine.
But as much as I enjoy how the game looks, it feels wrong. There's something special about original Half-Life's blocky 90's interiors, and remake looses some of the charm and atmosphere it had.
Xen is something that many people have praised in Black Mesa. I'm not one of them. Sure, it's beautiful (when it's not running like piece of poop) and it's fun to see more of the alien world and how life there is, but for me the original, short and focused Xen is perfect ending for Half-Life. Black Mesa's version is long, sometimes boring, focuses too much on fighting and as mentioned before, it runs very badly so playing it wasn't even that enjoyable..
My overall impression of Black Mesa is little bit confused. At the beginning it's seems that there's much work and love poured into it but the longer you play and closer to the end you get it starts to feel less like a remake of Half-Life and more like a mod. But It's a amazing work anyway even though I didn't personally liked all the aspects of it.
