Kowalski's reference has loads of canned openers (The Art of Approaching from
www.scribd.com).
I do both natural and canned.
Natural for me is usually a bit smoother (when it is more or less natural), but sometimes when the context is more challenging I find it tough.
eg, when there is a seated set or something I really struggle with coming out with a natural opener. I think to myself – what do I say?
So in some situations I really struggle with natural openers, and I find opinion openers work really well. Success in the sense of (after a few minutes of ditching the canned thread) going on to make a connection with non-canned conversation, and a number close and meeting up for days two and onward. I'm not too good at one-night kiss closes just yet.
I've yet to see anyone open as readily using natural openers, especially in the above situations - If I see it, or learn to do it myself better, then I might make the switch to natural only content.
Anthony