I have an MBA, which has served me very well. I am now looking at going to law school (I'm a mid-career changer). It all depends on what you want to do with your career. Having an MBA, and hoping to become a transactional Tax Attorney, the MBA is an excellent degree to have in that you are able to understand complex business issues more so than just an attorney. I work with attorney's all the time in my field, and sometimes, they just don't get the business end of things. Not that they are not intelligent, they just don't have the same level of exposure to different business issues that an MBA will give you. I wish I had done a joint MBA/JD, because now, I wouldn't be looking at spending another 3-4 years in law school (I plan to pursue an LLM if the economy is still in the toilet when I graduate). My advise, is to determine which field of law you are going to practice in. If you are going for litigation, then I would argue that the MBA probably doesn't make a lot of sense. However, if you plan to do banking, M&A, or tax/business law, by all means, do yourself a favor and get the MBA/JD so that you can be a greater asset to your future clients.
Just my two cents.