Vantaggi
High-profile matters, well-connected firm, lots of talented people and good opportunity to make great connections. Though it may not be the #1 most prestigious firm in Boston, this is still the "big time" in terms of law practice, and you'll learn a lot just by keeping your eyes open.
Svantaggi
Working in a large law firm can suck at times as they are all very demanding, and you can't really establish any power within the firm unless you develop a big book of business. So you need to stand up for yourself and make sure you don't get pushed around or mistreated by any partners or anyone else as an associate. If you go in ready to walk out and leave at any time (not being wedded to the idea of having to make partner), you'll do fine. And if you develop your own book of business, which you should over time, you'll do well whether you stay or go.