Pros
Workday is truly re-inventing how ERP systems work. Having been in ERP for 10 years, there is the opportunity to make business processes more efficient utilizing object modeling. That coupled with being SAAS makes for some interesting work. Workday is really telecommuter friendly; they don't care where you work as long as you are available and you meet your deadlines. I do believe the founders of the company want people to enjoy where they work. Lots of company events, a couple of game rooms, and people joking around make for a good environment even with the high workload. (The CEO does expect you to work). Certain departments are more stressful than others.
Cons
Health care and 401K options are disappointing; I've had better at other companies this size. Also the corporate culture can wear on you over time.