photography on the net forum is not a Canon fanboy site.
Is a site set up by Pekka Saarinen specificity for Canon digital camera enthusiasts, that's why it's full of Canon
fanboys 
and to be honest probably the best forums on the net if you have Canon gear.
There is the much improved IS system Canon have over what the MK I had too, but yes the mk II is a better lens all round.
I'm over 50, I
NEVER go to the gym, I don't use a tripod, and rarely use a monopod (sometimes if I have the extender on the 70-200 or using a 100-400) yet I have no problem carrying and shooting with my 2.8 IS on a 1D mk IV body, all day at track and field events.
You have been believing too many reviews there

yes it heavier than a f4 L, but some bright spark will come along and say get a 55-200 because it's lighter than an f4 L lens. The weight really should not be an issue for anyone without underlying health problems. IMHO
I do agree if your
never going to need f2.8 then why waste your money, and with new bodies get better at very high ISO less people will need 2.8, then just get the f4, but some folk need the f2.8 or want that bit more background blur it will give, to be honest if I could find and afford one I would have a 200 mm f1.8 L

well the Canon EF 200mm f/2.0 L IS USM really