Pros
Gives an opportunity (albeit painful) to see how not to run a business. Shows you what happens through every layer of the company when you hire low-calibre managers and directors who talk the talk but fall down on delivery. This really helps you assess how good other firms are before considering taking up a position; it should also help if you are planning to start your own consulting business.
Cons
Don't want to labour the point here as I think that there is universal acceptance that Frost & Sullivan is a very poor firm in terms of working environment, professional competence, and profitability. I'll try and resist the temptation to rant and distil the main downsides into the following points: 1. The firm has very poor profitability and no properly managed cost control - they have been struggling for a number of years, even in the good times (alarm bells should be ringing) 2. The sales culture creates selfishness that is corrosive 3. Lack of focus on high quality delivery - focus is on sales 4. No real direction or professional competence in one particular area 5. The firm has developed a reputation for attracting poor quality individuals 6. Client dissatisfaction - the worst possible outcome in consulting 7. Poor pay - the firm generally doesn't really look after its people