Short and simple: If you like the original Half Life or are interested in playing it but want the best possible version of it, play Black Mesa.
Crowbar Collective did an excellent job in taking a existing game and turning it into the best game I've played this year.
I've replayed the original before starting Black Mesa and without a doubt, they absolutely improved on pretty much every detail. The puzzles, while still being a bit of a drag, are much more interesting. The weapons feel better, punchier and with better sound effects. The level of detail is much improved since the original hardware limitations aren't there anymore, as they were when HL was developed. The sound effects are what you expect from an HL game but with massive improvements to the resolution of the samples. I'm not sure if they got the original samples in higher resolution from Valve, but they are spot on, when it comes to most of them at least, including the voice samples. The gun samples were definetely changed out, which is a good thing. Last but not least the graphics... My god, I didn't know the Source Engine could be so pretty. The lighting is such an upgrade over pretty much any Source Engine game I have ever seen.
People that haven't played HL yet should stop reading:
Xen is beautiful. It's like Michelangelo was only given crayons to draw and then whips out the Sistine Chapel. Absolutely amazing!
The Nihilanth fight was a bit chaotic but very interesting. I thought it could be a bit more obvious what to do but it was still a better endboss than anything I've seen in the last decade.

My verdict is: Buy it and buy it now! It's worth every penny!

Short and simple: If you like the original Half Life or are interested in playing it but want the best possible version of it, play Black Mesa. Crowbar Collective did an excellent job in taking a existing game and turning it into the best game I've played this year. I've replayed the original before starting Black Mesa and without a doubt, they absolutely improved on pretty much every detail. The puzzles, while still being a bit of a drag, are much more interesting. The weapons feel better, punchier and with better sound effects. The level of detail is much improved since the original hardware limitations aren't there anymore, as they were when HL was developed. The sound effects are what you expect from an HL game but with massive improvements to the resolution of the samples. I'm not sure if they got the original samples in higher resolution from Valve, but they are spot on, when it comes to most of them at least, including the voice samples. The gun samples were definetely changed out, which is a good thing. Last but not least the graphics... My god, I didn't know the Source Engine could be so pretty. The lighting is such an upgrade over pretty much any Source Engine game I have ever seen. People that haven't played HL yet should stop reading: Xen is beautiful. It's like Michelangelo was only given crayons to draw and then whips out the Sistine Chapel. Absolutely amazing! The Nihilanth fight was a bit chaotic but very interesting. I thought it could be a bit more obvious what to do but it was still a better endboss than anything I've seen in the last decade. My verdict is: Buy it and buy it now! It's worth every penny!