I don't really know myself. There have been times where I have watched people say nice things to people they don't know and it has been cringeworthy to watch. The recipient normally smiles awkwardly and moves along as quickly as possible probably thinking that the person who has complimented them is some sort of sexually frustrated leper, while the complimenter spends the next hour wallowing in embarrassment and self-loathing.
On the other hand, on the one or two times where I have been complimented, it has genuinely made me feel better about myself, and I am happy for the rest of the day.
I'm pretty sure I'd be right in assuming that being nice is an awful way to start a conversation/chat someone up, but would people say that they find it in general nice, or just think its weird?