There's is alot of talk about Half Life being a movie in a sort of 3rd person view. Meaning there will be several viewpoints from the scientists, guards, soldiers, alians etc. Plus it gives you infomation and stories that the game never had giving it a complete feeling, well that is the theroy. This is excellent as in the HL games your mostly fixed to one viewpoint. Best part is there can be an easy sequal so a real moneyspinner can be made, just hope that theres a damn good director.
The only con is set costs and casting will make it one of the most expensive films of all time, though if they pay their cards right then it may well be one of the best films of all time.