I saw the best St. Patrick's day marketing by Guinness while I was in France: SymPatick Day. Oh man, I wanted to rip the poster down and take it home to show everyone it in all its witty phonetic glory.

One of the differences I think between England and Ireland, though, is that Ireland is viewed as a nation of alcoholics, specifically Guinness-drinkers. There isn't quite the same opportunity to exploit St. George's Day for a day of drinking by English breweries. But give a few years, the stereotype of the English as violent, louty binge-drinkers is setting in well.

I don't actually celebrate either, although I do indulge myself in a rut of pseudo-Irish cynical outrage every March 17th. I guess you could call that a form of celebration.
I'm completely of very recent Irish descent, but I grew up in England with parents who have English accents and although I spend a lot of time in the English-Irish community when I visit my family at least, I see myself as English. My whole irritation at St. Paddy's day celebrations comes from the fact that the day itself is hardly being celebrated in honour of Ireland.