I wouldn't call them cons as much as challenges. The company is growing very quickly right now so it's typically a very fast paced atmosphere, which makes it feel somewhat awkward and/or stagnant when production occasionally slows from exponential to "average". The challenge there is retaining a big-picture mentality when everything suddenly isn't lightning-speed. Patience, grasshopper, patience.
Another challenge (depending upon how you see it) would be that it might become easy to get discouraged if you don't excel as quickly as your coworkers. Greenspire will absolutely develop employees at their own pace, but I've seen several people give up when they aren't top performers within their first week (hence my earlier point).
Ultimately, a great company for the thick-skinned, ambitious, and entrepreneurial.
