Pros
Okay, I'll cut to the chase first off and state that I think that at least 90% of the negative reviews here were written out of either haste or carelessness, as I am definitely NOT a member of the HR team at TRI (which I have seen some posts accuse positive ones of being), yet just left the company last week after having happily and proudly server as a team member for almost 6.5 years. I loved my time with TRI and am forever grateful that I was able to make a complete career transition by joining as an entry-level Medical Writer...a starting position which transformed into promotion to Medical Writer III by a year before I departed the company for purely personal reasons. At TRI, the employee essentially sets their own boundaries: you can fly as high (or as low, though within the boundary of making acceptable contributions to your role) as you want. Opportunities for career training are abundant, as are opportunities to work across groups (including internal business development): both contribute significantly to personal fulfillment and/or advancement, and to be honest, I don't know of many companies that offer such an enticing combination. These are not forced things, either, but merely offered and (in my personal opinion) too good to pass up participating in. Other "pros" include that it is extremely easy to get to know everyone in the company (at all levels) if you are enthusiastic enough to care to get to know them!
Cons
I can't really think of any flat-out "cons" to post. This was my first corporate experience (I'd been a lab-dweller to the point that I first joined the company), and I thus regard all moments there as learning experiences.