Pros
Semi-relaxed working environment.
Flexible start/end times (10pm starts ideal for dropping off kids at school).
Wide range of technologies (C#, Delphi, Java, .NET, Ruby, Oracle, MS-SQL).
Great pool of available collective knowledge.
Dominant player in field.
Working with some very large organisations.
Worldwide travel.
Great regular paid social events (includes ones with families - e.g. annual weekend at CentreParcs - all paid).
Paid Gym and BUPA membership.
Cons
Too many staff birthdays... too much cake, too little time.