Pros
DM has some serious perks: company amex; breakfast, lunch and snack time served (before the downturn); employees entertain hedge fund clients at really fun events (clubs/restaurants etc). Work for a researcher is uncomplicated - becomes boring REALLY quickly. Overall though you feel as though you are part of a great family so the tight knit culture makes it a great and fun place to work.
Cons
Not great work life balance. You get sucked in to doing EVERYTHING DM. Every night of the week is an event you are expected to attend till ludicrous hours (midnight-4am) and be at your desk by 7am the next morning. Almost no ability to grow within the company. Ive seen employees stay for years and get next to no promotion or a false increase in title with no increase in responsibilities or pay.