I use this ALL the time., It's like my "last ditch" option when I don't really have an opener and need to open NOW. Generally, dunno why (and I never thought of this before now), but I happen to use this on single targets that I've seen in the past but never had a chance to open until just then.
I generally say something specific though to enhance the realism of it.. like, "Hey, I see you here all the time (leave this out if you havent seen them here, duh), is your name kimberly?" then she'll say no, or it'll happen to be her name lol (this has happened to me more than once and it's pretty hilarious to see their reaction, I'll actually play the game in my mind to try and guess their actual name and I would say 5-10% of the time it works.. kinda weird) anywho, then you can be like "oh, heh, my bad, you look like this girl I used to know really well named _________ and I thought i'd say hey." Then you gotta transition faster than hell or you'll lose it and you'll lose it fast -
So the only downfall is you gotta jump straight into something else. Once the girl has it in her mind that you're a complete and total stranger, she may put up some shields - thinking along the lines of "cool now I can keep to myself since I don't know this guy" - depends on the personality of the girl. But, if you want it to be successful, the opener has to be followed up with something kinda interesting/entertaining pretty quickly or else you'll lose it. That's actually kind of a huge downside. If you have the confidence level to do this with girls, you almost might as well consider direct game - "I see you here all the time and you're actually pretty cute, but I've been wondering if you're as smart as you are attractive

" or whatever.
So yeah, I use it alot. It's a great OPENER. That's all it is though. It builds no rapport, no DHV, no DLV.. Great opener for those with AA to practice a bit. I've also used this from just seeing a girl from behind, she was a 8-9 from behind but holy shit her face... yeah.. no. bad news. easy to get out of there if needed =D