I have the "Tamzooka" and upto 400 I am extremely pleased the sharpness, contrast etc. Above 450 it gets a wee bit soft - not much but when the frames are side by side it is noticeable.

It is not exactly a joy to hand hold. The collar foot makes it easy to carry (rotate to the top/side and off we go - depends on how you want to carry it and try to swing it into action LOL HA)

Adding another two pounds is really pushing the hand hold idea for very long. Lots of breaks in the action.

Having said all of this - I am 5x pleased w/ the 50 1.4 art - Wow what a beast in all regards. If they have pulled off something even vaguely close IQ wise these will be flying off the shelves. (then again any lens with those specs would).

Just my 2 pennies