Pros
Groupon has two IT hubs in Europe. One is in Berlin and the other is in Dublin. Currently I am working in the Dublin city centre in a backend Java environment I have been working in Groupon for only a few months but I love it due to the scope of projects that I can work on. (Groupon is much more than just a daily deal website) there are 12,000 people working in Groupon worldwide and this is phenomenal for a company that is only 6 years old) I work with top engineers that came from larger Tech companies as Groupon offers more freedom to be creative and to sculpt a career. Groupon is still in a start up mode but the company is stable and cash rich. The salaries are very strong along side the benefits (Health, sick pension etc)
Cons
The weather in Dublin is not great but I am looking forward to the summer