I think that D3 is very nice looking and even though I had the game since it came out, I bet I have only played it for about a hour. I just cannot get into it even though it runs perfect on my system.
I really enjoyed HL and have the HL2 Collectors Edition pre-ordered. I will definatly play through the single player of HL2 and HL (on Source Engine) again but my main reason for getting it, and you can prolly tell by the bottom of my sig, is for the multiplayer and more so, CS:S.