Why or why not,and if not why?
Yes, but always early on and always when making physical contact. If they look good, I'll go for the greeting hug, separate while still making contact with their arms (slowly releasing the hug w/ hands grazing their forearms elbow) and tell them "You look very nice" with pleasant look while stepping back for a look. Key here is pleasant look not a goofy ass smile like you hit a come-up.
Why? I'm a big believer in establishing yourself as someone who's comfortable with being physical and appreciating femininity early on. Women usually know if they're going to have sex with you within the 1st 30 minutes to an hour of a date. Starting like this helps you cement yourself in the "I think he has experience. He knows what he's doing." category. Women have told me as much.
It also takes the pressure off of providing a compliment on looks the rest of the date. Which can put women a little off balance (in a good way). OK, we know you're attractive and got that out of the way - with that box checked it can kick off a little tension in them about what else they bring to the table. Which I like and think separates women into hit and quits vs. women I'd actually date.
Just my two cents though. Try it out young brehs.