I don't have a case or screen protector. Going on 2 months with the Maxx, and all is well.
A case is a YMMV type deal. If you're prone to the dropsies, then it might not be a bad idea to get one for added protection. However, a case is no guarantee that your phone will survive a fall, and it does hide the look of the phone (especially if you get a black-brick Otterbox or something in that vein). Some are so thick, it makes owning the thin Razr pointless. And, in my experience, a case can cause cosmetic damage its trying to protect against. On my Incredible, the edge bezel actually got scratched up from debris getting between the case and the phone. So, its your call, but personally, I'd rather just pay the monthly insurance for a year or so.
As for a screen protector, I had one on my Incredible as well but don't have one on my Maxx. The Maxx does have Gorilla Glass, so you have some scratch protection there already. I feel the SP is just redundant. Just my opinion.
In short, if you're one to re-sell your phone when you're done with it, taking the extra protections might be wise to keep the phone as pristine as possible. Otherwise, just try to be careful and enjoy your phone!