D5100 LCD unusable for manual shooting...should I care?

Sounds pretty poor, I think in general Nikon DSLRs are poor in live view. I don't think that this is a case of crippling (like D7000 small buffers and lack of AF-ON button) rather that people who buy DSLRs don't generally use live view much. I think that if you want to shoot in live view then you are probably better of not using a DSLR.