Let me preface this by saying that if one of the 'pros' above works for you, do go ahead and work here for a while, and make up your own mind. Of course, always make sure you can leave if it doesn't work for you. I don't work there anymore, but I gave myself a year before composing this, so that I could be objective, and avoid looking vindictive.
With that, let me begin ...
#1 - Legacy code -- you must have heard this term thrown about casually, or in the titles of books you might have passed by -- but you will be working with legacy code that could be 10 or 20 years old. Now thats not a bad thing in itself, except that a whole lot of it was written by incompetent people (more of this in #2). I see you're not sufficiently scared yet -- I have three words for you -- "GUI in Fortran" -- if that doesn't do it for you, go ahead and send in your resume, you'll love the place.
#2 - Incompetent people -- they're all over the place -- it could be your colleagues, your managers, sales people you interface with. Part of this, I think, has to do with the broken recruitment process - I won't necessarily blame HR, rather the seemingly ad-hoc nature of the actual interview process itself (e.g. asking textbookish "what is a singleton?" instead of "Solve problem XYZ" self-selects the kinds of people that are unwilling to learn new stuff -- add them to a bunch of old-timers who know a lot of old stuff, and you have a potent mix).
Around the time I left, company policy removed the criteria of having a computer science degree for being hired as a developer -- read into this what you will.
I felt this people factor made everyone excessively paranoid, since, unable to rely on reason for how things should work, they were often reduced to superstition ("don't touch that code -- copy-paste it instead and put it on a flag instead!" -- rinse and repeat, and you have spaghetti code the likes of which you cannot imagine -- unless, of course, eventually, inevitably -- you have to fix it)
#3 - Opaque work environment -- I never had a clue why we were doing what we were doing, or why we stopped doing it and began doing something else. Mysterious communiques were occasionally delivered once a year, and then ignored in the actual work ordered throughout the year.
#4 - Poor software principles - I was gonna lump this in with #1 or #2 but it deserves special mention since it encompasses and encourages both of them. Expect to waste days, weeks (months ?) doing monotonous work, only because people are unwilling, unable (or both) to do things differently. The excessively proprietary nature of *all* software means that not only are you forced to rely on substandard code, but also have to do without tools that are commonplace elsewhere ("What's that fancy svn/git thing ? We use RCS!" (Seriously))
#5 - Weird billing process - at the end of each day, you're required to 'bill' time to a 'ticket'. Ok, nothing wrong with that. When I joined, I had no work for about two months -- I still had to bill time -- what's more, I saw that a couple of older employees in my team, actually *did nothing* and billed time to tickets they 'owned' for a long long time. This was quite bizarre at first, but after sufficient time, I internalized it and became a certified slacker myself.
#6 - Top down review process (actually, top down everything) - Your manager has the first, last and only say in what your performance was. Period. (The rest -- employees sucking up to their manager, going behind their colleagues' backs to talk to managers, stabbing said backs etc. -- follows from this)
[Caveat here: I didn't really see #3, #4 and #6 as terrible things until I moved to a different place where I had transparency, good tools and some kind of peer review, and was able to draw some contrast. I'm told that most banks are similar, and so in that respect, Bloomberg is certainly "no worse" than many places]
Finally, I must confess to a soft spot for the place, it being my first employer, and in any large organization, no narrative can successfully capture the small details. My manager was ok with time off and sick days, and not (unlike some reviews suggest) scary, intimidating and excessively micro-managing -- but yes, I did observe (both first-hand and second-hand) other managers doing the same, and I will happily admit that I fared better than most.
