I installed a Troy MRF-C 7" on my Bushy M4 Patrolman and I love it. I did a lot of research and noticed that on many of the cross-sections of the rail extrusions used by others were lacking support in critical areas, especially where the rails 90 into the circular portion of the extrusion. The Troys are nice and beefy in that area and seem to have a uniform material thickness around the whole cross section of their extrusions.
Take a look:
http://www.militarymorons.com/weapons/img/mrfc4.jpg
Also, the bottom of the rail comes off easily for cleaning just by depressing a locking button, but it feels like one solid piece when all together. Beautiful machining, anodizing and white reference lettering. It also has four anti-rotation lugs that fit on each side of the upper receiver to prevent the fore-end from being torqued and possibly de-nutting your barrel, which is important especially if you are using a broom stick handle on the foreend.
Military Morons deserves a plug for their really nice review of various rail systems:
Military Morons
Good luck!