(1) You need to have a specific purpose for being at B-School, and "I want an MBA" is not nearly specific enough

(2) You need to match your purpose to the school you go to. If you want to be an I-banker, don't go to the local college that offers an MBA, you need to be at a school that has connections to the banks on Wall Street, both from an alumni perspective and from a placement perspective.  The same logic applies to any other career path-go to the school that can open doors in that path 

(3). Unless the reason you are getting an MBA is because it is a requirement for a promotion in your company, Top Ten schools matter and matter a lot. With any of them you will open up doors and a network that will get you where you want to go.  If you go to a school that is convenient due to location or cost, you will likely find that you don't really change your career fortunes too much.  Doesn't mean there aren't schools outside of the Top 10 that aren't good (BYU is one of them), 

(4) The "Top 10" is a list slightly larger than 10, but there is a very clear pecking order in B-Schools.  Any rating system that doesn't have the Trade School on the Charles (aka HBS) as #1 with Stanford and Wharton right behind is selling a bill of goods.  Those are the 3 premier schools and are globally recognized.  Behind that is a group that includes Dartmouth (Tuck), MIT (Sloan), UVA (Darden), Northwestern (Kellogg), Duke (Fuqua), Colombia, Cornell (Johnson), Michigan (Ross), Chicago (Booth).  Each of them provides a different set of opportunities (eg if you want to be in Hotel Management, Cornell is the place for you, but not a good option for Wall Street), but almost all will provide a very good business network (not like HBS, but very good).

(5) B-school is much less about the academics than it is about the network and placement opportunities.  There is very little taught on an MBA course that isn't similar to what is taught in an undergrad business course.  It's one of the reason why Business majors are relatively infrequently admitted to the top schools.  If you think you want to do an MBA someday, don't do an undergrad major in business.  Whatever you major in, make sure that it can demonstrate your abilities in quantitative analytics, in communication and writing skills, and in abstract thinking skills.  An English lit major who learned to analyze poetry and coherently write about it and tipped it off with a minor in stats is a great candidate.  A English Lit major that only dealt with soft-side things and never took a math class will probably not even get a look by a top school. 

Of you do an MBA for the right reason at the right school with the right expectations, it will be great.  If not, you could regret the decision.