Pros
You get to work with a wide variety of technologies and motivated young people who are trying to solve interesting problems. Beer every Friday. A constantly rotating cast will give you opportunities to climb the ladders quickly with the slightest demonstration of expertise.
Cons
Where to begin ... your first day, you might not have a workstation at all -- mine didn't arrive until I had been there a week, and the invoice in the box said they hadn't bothered to place the order until the day after I started. (This was 3 weeks after we had agreed upon an offer and set the start date.) Once you have a workstation and a desk, you can expect to spend a few days a month tearing it down and setting it up again, as the company only rents out the cheapest room(s) in the building, which changes periodically. Critical services like our bug trackers were periodically offline for days at a time because someone forgot to pay the bill. The internet was down an average of 5-10 work hours/wk. "Flow" is an unknown concept to this team. You can expect constant interruptions from coworkers and managers alike. They call themselves "Agile" but in this case it means "absolute mayhem", as people are often asked to switch projects multiple times a day. (My personal record was 5 in a day.) Unsurprisingly, nothing gets done when nobody can concentrate, so there is an unspoken 50hrs/wk minimum, which will earn you scorn if broken. (The company's internal slogan is "Get it more" which barely bothers to veil the message of "Work harder.") You'll get beer in the break room on Fridays, where you'll have time to ponder the posted warnings that employees are subject to lie detector tests at any time. Finally, don't get sick or injured. If you do, you can expect to be let go, possibly without pay. (This happened to one of our contractors.)