Hello, This rude and uncultured person will endeavour to answer your question to the best of his imperfect knowledge. In a country where formal toasts are ported, it would be inappropriate to swirl before the toast. This is the one limitation that should be kept in mind at all times.
Also, in the words of a maverick poster who has not been seen in the vicinity for along time, " it is fun to see how fast you can swirl the wine without it spraying over your neighbor".
On a more serious note, when drinking older wines (I quite often drink and enjoy rather old wines, mean vintage c 1960), it is interesting to compare the olfactory sensations frist before swirling, then after - the pre-swirl bouquet often being much more fragile and delicate.
HTH
Cheers
Nils