We love Venice so we go every year for 10 days to 2 weeks. Not a day goes by that we don't spend hours entranced by San Marco. However we try to avoid it between 10AM and 9 PM because of all the cruise passengers and tour members standing around. early and late it is a very spiritual and beautiful place. The city still has not gotten rid of the annoying rose sellers but it is worth avoiding them to be there. If someone approaches and offer you a "free rose" ignore them. It isn't really free. They will hound you till you make a "donation" to some "charity" in India.
Sometimes we go really late, after all three orchestras (which are quite good) finish playing and we have the whole square to ourselves. those are the really special times. Listen , look around imagine what it was like 400 years ago. The wealth and power of Venice in it's peak are very impressive. The fact that it was actually a near democracy is very comforting.More