My point, for those who have experience with those particular ILS approaches, is that following them with the autopilot on is akin to a Six Flags roller coaster. Very unreliable/sensitive below a certain altitude. We fly them by hand to reduce the significant aircraft oscillations as the autopilot chases the signal (in fact, I believe that is a charted requirement on KMRY). Never had a GPS approach do that. My observation was simply that not all ground based navaids are rock-solid guarantees, and knowing what I know about those approaches I would not be gung-ho hand flying an RV down to minimums there.
Can you lose GPS? Certainly. Particularly as one pointed out, in the vicinity of military test areas. Once got jammed in the vicinity of White Sands at FL370. Ended up getting radar vectors from center, rather than instructions to join a V- or J- route. But my jab at those broadly proclaiming that Commercial Passenger craft do not rely on GPS so you shouldn't either are frankly wrong on both counts. Leaving aside the fact that 121 requirements are significantly more stringent on redundancies for obvious reasons, not everything out there is a 767 that rolled off the line in the 70's. I've flown 80 hours a month on average for work over the last 15 years, and can count on one hand the number of times I lost a GPS signal. The handful of times I've gone to mins on an approach in the last year, it has been to CAT II mins and/or in icing conditions or high crosswinds, so I wouldn't be flying recreationally then anyway. So I feel pretty confident that I don't need the weight or expense of a NAV radio in my RV to supplement my WAAS GPS.
End statement: Put in a VHF radio if it makes you feel good, but don't tell me that it is certain that you'll be dead in the water if you don't have one, just because...