The Micor Leader honestly does not do much for me. It is a solid enough design, but nothing that truly sets it apart from the competition in that market.
If you have the cash for a semi .50BMG, and you want a bullpup, the GM6 would be the way to go.
If you can deal without it being a bullpup, the Serbu is the obvious choice, despite the small problems with cycling. (*these problems were fixed for a grand total of $140.00 in gunsmithing fees, and another $300 to tune the trigger, extractor, ejector, and magazine, turned this gun into a firearm that is more effective and accurate than the Barrett M82A1.)