This is the lens with the open rear area and the little glass filter that fits in a slot towards the back, right? If this is the same lens then the only thing I'll warn you about is keeping that open area in the back extremely clean and dust free because it will fill your mirror box with dust and junk if you don't. Other than that, it's a nice, albeit, big and heavy lens that looks like it would easily absorb a direct hit with an IED.
Also, make certain this lens comes with that little filter insert or be sure to buy one before you use it. Otherwise it's the same as running around with an open camera with no lens.