Do not have an MBA, but many friends who have gone to the top 3-5 schools, as well as some who did eMBA/part-time MBA programs.
There are a few worthwhile reasons to get an MBA, but one really trumps the rest.
As some others have said, the overwhelming value of an MBA is to build strong relationships with future business leaders. End of story. If you don't want to spend 2 years doing that and pay for it, don't do an MBA.
Those I've talked with that did an eMBA mostly regretted it because they were incredibly busy, and barely had time to meet anyone in the program, let alone build strong relationships with them.
If you don't have much background in management or business (most of which you can get from reading books) the course material will be helpful, but you could just as easily learn it on the job - if you can get the job. That is the other reason to get an MBA; to get into a company who requires it, though these are increasingly become less mandatory.
There are many answers to the question of how to get to executive management, but I think a very common one, which is likely to work for most people is the following: work at a service provider which gives you some strong functional/business skills (e.g., consulting, investment banking, equity research, marketing strategy, etc.). Do well there, but don't stay too long. From there, take a middle-management role (e.g, director, VP) at a corporation that is growing fairly quickly. Make your way up, and probably switch to another firm if you're not advancing quickly where you are.
Be careful of the trap of not having operating responsibility - you won't have this as a consultant or investment banker. If you don't have experience owning a P&L, you can't be trusted to do so even if you smart and capable. You could be in corporate strategy, corporate development, etc. but those are not true executive management roles.
Wow that went longer than I intended so I'm going to stop rambling.