My first 645 was an original 645 model, very heavy and solid. I really like it but it does get heavy when lugging it for long periods. I have the CDS prism, with the famous horizontal line fault, but it has a metering fault, so I normally just use the waist level finder as I find it helps me compose more easily. Then I bought a second hand 645e and it's noticably lighter, nice viewfinder, and AE for when I'm being lazy.
Would love a 645PROTL but way too expensive, even on the second hand market.
(temporarily in Tokyo)