I wouldn't listen to 'dontgothere' if I were you. The hours are long, yes - but hardly different from anywhere else (and a hell of a lot better than my friends at Mckinsey!). There has been a really big effort over the last few years to turn around the quant-based, 'marakon hours =marathon hours' rep, which is reflected in recruiting policy - they are seeking more 'rounded' individuals, and offer policies such as the 11 and 1/10 and 2 months year (ie you work 11 months and get 1 month of unpaid leave of holiday as well as your normal paid holiday, or 10 months with 2 off), which have been v popular. Have a look on Vault 'top 50 consultancies' section for a good, balanced view (they interview lots of consultants, some from within marakon and others from outside, and marakon does well in both reputation and quality of life sections)
The bit I would agree on is the current lack of name recognition. This isn;t too much of a problem within industry, or at higher levels, but is definitely something to consider if you just want to stay for 2 years then move on. Another point to be aware of is if you might want to go into government or political posts later - Marakon, unlike many consultancies in these New Labour times, do NO government work, so consider where you want your experience to be.
Overall, I would heartily recommend Marakon - it has truly fantastic training, nice workmates and as much of a balanced life as you can find anywhere in consultancy. This must be balanced with lower name recognition and a pure business focus, but for me, this is more than a fair trade. There seems to be one person on here who writes only very negative (and very dated!) 'quant-based' comments about Marakon - but then I'm biased too, so I would really recommend slightly more balanced and professional sites, or why not apply and see what you think of the office and the people you meet?