Vantaggi
Relaxed dress, generous travel allowances, free breakfast, good benefits. Culture seems much better in the UK than the US, especially in departments that fall outside of operations.
Svantaggi
Culture is very uneven and an unwritten class system of employees do seem to exist between countries, offices, and departments. Expectations also differ greatly between these departments. Some are expected to be available 24/7 while others seem to skate by. HR seems intimidated by senior management in the US and is therefore ineffective. In this same vein, some very questionable workplace behavior occurs which would not be tolerated in other companies, startups included. Moo seems like a great and fun place to work for entry level employees but I would not recommend it for more experienced individuals.