to short damn it why buy just rent it!
Now, on to the good stuff. The gameplay is awesome. There is the traditional shooter content, and some neat (although sometimes unnecessary) puzzles as well. The gameplay is awesome, as well...having Alyx on your side is super cool, and she provides good narration that progresses the storyline, and some laughs as well. Fans used to the classic "halflife moments" will not be disappointed, either. Also, there is nice progression of the story...but, as in Halflife 1 and 2, the ending raises more questions than it answers.
The graphics are very cool, and the game utilizes the new lighting stuff (i believe its the HDR stuff) very well. Sometimes, however, the lighting seems way too intense...I could often find myself looking at a flourescent lamp and half the screen would white out. Gameplay was also stable on my somewhat-dated computer (P4 2.8, 1 GB RAM, 128 MB Geforce 6600 GT) at 1024x768 resolution with HDR and settings on high.
Fans of Halflife and any mild FPS fan definately need this expansion