The game hangs in places when I play it and requires a CTRL + Alt + Delete "Sign Out" to regain control of the PC. If you look on SR4 fondly enough then still buy it because it is bearable if you want to play the game again. If you haven't played it before, I wouldn't bother. SR3 is far better in terms of story and game play and doesn't have what I consider to be the worst DLC of any game i've ever played.
I found the dialogue to be unengaging and there doesn't seem to be a way of speeding it up that still allows you to have some idea of what is happening. The combat system is equally a disappointment. I got as far as the first "Boss" fight in the sewer and descided that life was too short and gave up. As this is probably the last game that I will purchase this year, I can say that, for me, it is also the worst of the year. If you bought the game and enjoyed it, then that's all well and good, but i'd be seriously considering a different way to waste, I mean spend, £16.