Pros
Excitement and the feeling that there is technology being developed that will be shaping the future . The potential for exercising share options. Some excellent customers like Salesforce. Technology that looks and feels intuitive in client demonstrations.
Cons
This might just be a 'start-up thing' - but I found some major challenges. There is an awful lot of vapourware in terms of what is presented to the customer/partner, and what is actually happening/achievable, proven... this pushed me out of my comfort zone as a salesperson at times. Also the culture is entirely US-focussed, highly detached and quite often does NOT reward effort outside of billable seats. I found that this combination saw some fairly schizophrenic 'hire 'em and fire 'em' decisions, and I have since seen a significant slice of influential Management (Sales and Product) removed - but I know some guys there still working serious hours and finding life fairly uncomfortable.