Pros

high energy envrionment, and driven and encouraging workforce. Access to the executive team - even at the entry level positions. The envrionment supports cross postion/deparment communication. If I needed to I can and have written an e-mail to the VP of product and asked for direction/information and I am not at the executive level, and have gotten an honest answer and help.

 Relatively good work/life balance - set your own working hours, and flexibility with telecommuting - sort of... Good morale boosters, frequent team building and on-site training offered for development. The company still has the start-up feel, but the best way to describe it, is that it's growing up. Realizing that it's past its adolecence of 'start-up-dom' and trying to move towards a more polished 'business' perspective.
Casual wear in the office, and some good benefits & perks. (Earnest bonuses, expresso machines on sight, dot com shwag is common and easily pillagable, plus FOOZBALL!!! and lunchtime scrabble tourney's)

Cons

Being that it is a small/med sized company there are limited options for promotion and advancement within the same team/department. Although part of a larger company, it means that advancement may mean going to a partner company.

The hours lean towards the long, and there is little colaboration within in the groups, unless forced for a project. Eating at your desk for lunch is a regular daily occurance. The workload is large, and the project management is sometimes haphazard and break neck.

The business wants to get too much done on a shoestring. They can expect Lamborghini's and get stuck with Ford Fiesta's becuase of the lack of appropraite staffing and forsight. Marketing and Product teams take most of the gold stars... most other departments are adjuncts.

Advice to Senior Management

Consider that being 'scrappy' means that the tradeoff is going to result in a higher turnover in your core support departments.
Invest in different types (or longer) iteration cycles, and less of a focus on marketing.
Infrastructure is still essential to executing on ideas, and being nimble doesn't necessarily make a company healthy. For longer term sustainabilty think about what needs to be done to maintain, not just advance.