Most of the 1-2 star reviews encapsulate the cons well - take them seriously. A few more points to consider:
1) Very frequent org structure and responsibility changes with a growing "middle management" layer that really only functions to report statuses. With this, very little actually changes as far as decision authority. Even with a new CEO, Tom still calls the shots that move the needle. As the stock price and recent layoffs reflect, this model is broken.
2) During internal sales trainings, upper management consistently positions the C3 product suite as the most revolutionary and disruptive stack in the industry today - subtext being that Sales is consistently failing because they're not presenting value and past performance well enough to customers. Conversations with technical teams and market research show the product and application suites aren't significantly ahead of peers, and in many cases across the 130+ application portfolio, actually lag new entrants focused on a vertical capability.
3) Sales reps are lured in with a promise of high impact and appropriately high OTE. However, actual rep quota attainment is around 10-15% across Federal and commercial teams. Additionally, sales compensation is paid at cash collection, which is highly unorthodox and is something management will easily bend on if it means securing a deal.
4) On the sales compensation front, there were at least 4 reps on the Federal team in the last 2 years that were either fired before being able to collect commission or weren't paid IAW their compensation plan based on management discretion. I imagine there were many more claims across the commercial and EMEA teams. Since C3 settles unpaid compensation/commission claims via arbitration, none of these filings will show up on public record
5) To say the very least, the company's revenue recognition and accounting methodology is suspect at best. Every quarter there are prototype and slide-deck based SKU's added arbitrarily to deals by upper management in order to juice revenue numbers since these SKU's earn point-in-time revenue. However, these are misrepresented to the Street as recurring subscription-based earnings