I think for me the main issue is the lack of a decent search. Take for example buying a power supply from Newegg.com or Amazon.com:
I want a 750W PSU, made by Corsair, Seasonic, Antec, or NZXT with at least 4 Molex, at least 1 GPU power (8pin) and a Platinum efficiency rating.
With newegg I can set those filters, then sort by lowest price or highest reviews or re-evaluate the filters.
With Amazon I can search for 750W Power supply, and then maybe have some of the choices on the left, but not every vendor lists their product correctly.