I tend to marinade just to change flavor time to time. Bacon wrap always good. Olive oil/course black pepper/garlic/rosemary/ and yes time, will give you a very nice tasting meat on the grille or in the oven. Moderation in all spices generally will yield best results.
For the backstrap: I like to 1/4" cut dip in egg/milk roll in cracker crumbs and bake on cookie sheet at 400* flipping once till meduim rare. This is great.
However, the very best part of the deer: neck roast in slow cooker for 10-12 hours! It just don't get any better than that.