Philip gives his opinion of the new Zacuto Z-Finer Pro 2.5x ($375) and Pro 3x ($375) and the new Junior (about $250). He likes the Pro 2.5x and 3x, and seems to prefer the 3x, though he says it's very close and he likes the 2.5x for some things (the number refers to the magnification.) He particularly likes the new anti-fog glass on these models.
He doesn't like the Junior as much however, particularly disliking the mounting frame, and thinks that pretty much everyone should get one of the Pro models.
For those looking for a really cheap alternative, today I saw (and tried) the LCDVF viewfinder, which is $180. It attaches using small magnets and, like the Junior, does not have a diopter, so it isn't much use to me, but if you're looking for a viewfinder viewer at rock-bottom prices, this may be it.
Philip Bloom: Review of new Zacuto Z-Finders