Apple

The challenges are unparalleled. The environment is fast-paced and quirky. Cool, cool people abound! The Marcom folks have unequaled taste in hipster music and the latest fashion trends. It's APPLE! What more could I possibly say?! The cafeteria is awesome, too (especially the sushi!).

I would say that there are two.

The first is that the work/life balance really can suck. Part of this is an individual employee's responsibility -- you need to fend for yourself and unplug when you can. Part of it, however, is a culture of workaholics and burning out.

The other downside is the top-heavy management and proliferation of needless meetings and email. It's a drag on everyone's time and a constant annoyance.

Hire more good people so that the ones you have aren't so overworked.