Pros
At the office where I work, work is pretty flexible in the sense that it you need to work from home some day or if you need to work flexible hours, it's fine most of the time. In my area, services, you get to travel quite often, which is nice if you like the opportunity of travelling, but sometimes can be a little too much.
Cons
The number of promotions inside the company looks minimal. They don't usually disclose how many people are promoted, but my perception is that very few people are. The only exception was 2012, when many people were promoted and they decided to send the promotions information to everyone in the company. All other years had no information on number of promotions and it looks like there were very few. You better join Aspentech at the top of your career and don't expect to go much further.