The culture. If you're attempting to grow up, and take your job seriously, then you'll feel incredibly out of place here.
Unfortunately, once you strip the fun culture away, it reveals a company with many, many internal flaws that is only holding on because their income structure is incredibly lucrative. This become even more clear when Sykes took over, because the vision of the two companies doesn't line up very well.
The commission structure is awkward. Your commission percentage is based on the performance of everyone else on the floor. If you have a particularly high performance week, then you're pushing other people into earning a smaller percentage.
The hours are horrid. Many new hires find themselves on evenings (usually 11:30 - 8pm or 12:30 - 9pm) which on its own is acceptable, but it's made worse by the fact that they hold your weekends hostage. Getting a true 2 day weekend is a privilege reserved for long term employees. Your days off are usually 1 weekend day, and 1 week day, and they'll never give you Friday/Saturday or Sunday/Monday as those 2 days off. Most likely you'll see yours as Friday/Sunday, Thursday/Sunday, Saturday/Monday or Wednesday/Saturday and you've probably got a year before you're allowed to have the 2 days in a row off that you've taken for granted at every other company.
As I mentioned in the "Pros" section, the compensation is fantastic for top performers. Unfortunately, on the flip side, I've watched many average/aspiring sales reps become unmotivated and quit because of poor compensation, and then not getting any attention from coaches. If you're not generating enough revenue, then they have little interest in helping you improve. They'd rather just pressure you into quitting so that they don't have to worry about you any more.
Moving up in the company is a bit convoluted and secretive. If you get on upper management's good side, and golf with the right people, you'll pretty easily find yourself in a cushy salary job. They claim to reward performance, but in my time at the company, it always felt like a Boy's Club with a strong "bros before numbers" attitude. I feel like this is exacerbated by a poorly defined chain of command, so you never really know how to move up until you already have. Interviews from internal applications feel very patronizing, because many people interviewing you don't even hide the fact that it's just a formality and they've already made their choice to promote a friend before even posting the listing.