I still have them both, and MBAM 1.50 Beta was released today (see my thread posted today). While there may be arguments over process issues and such, that doesn't matter to me. MBAM does scan 64 bit files, I use the product weekly, and see the x64 files go by. MSE is still (for the time being) my first line of defense, followed by MBAM, followed by the free ESET online scanner (a very deep scan, it takes an hour and a half to scan my system), and finally SAS to clean up the tracking cookies. A decent, free, 4 program approach, as noted, one cannot pick up everything alone.
It takes an proactive approach to keep your computer clean as possible, and I'm not referring to the dust on it. Your OS(s), programs, emails, files, etc, needs a complete scan weekly with at least one product, your AV of choice or MBAM is a good option for this. The ESET online scanner is, too. SAS is good to run once monthly for cleaning tracking cookies.
Keeping your AV of choice updated and running regular scans is a must for any computer user. MBAM is a great second line of defense for anyone, 32 or 64 bit, it doesn't matter, it works fine on both platforms.
Cat