Without autopilot is fine provided the flightplanning takes that into account (non RVSM, alternate etc). Absolutely no problem to fly without it. GPWS is a bit more tricky and it actually depends on operation. However it is quite possible to fly without doing a CFIT even without having a GPWS active. Granted, most pilots used to it would be startled by the missing auto height callouts.
Actually, just checked my MEL and it allows dispatch without Decision Minimum Height Selectors, you just have to make sure that you use an approach that doesn't require its use. Basically you are restricted to VFR flight or visual approaches.