I was provided this product for review. I was not given compensation do to so, and it was made clear that my review will strictly be my own truthful thoughts, no promises made as to the positivity or negativity that i may express.
Viewfinders range from dirt cheap, to silly expensive. This one sits right in the middle, but has a lot of features/adjustments and a build quality that i would attribute closer to the higher end units
A nice mix of metal and thick plastic. Looking at the unit, it's clear the engineers know where it's appropriate to use either material. Other high end units may have a more refined feel, but i'm perfectly pleased with this unit's construction, especially considering the price.
A good amount of adjustment in all directions, matches up to my 5d2 no problem. Since most DSLRs have a pretty similar screen orientation, it should work all around. You have thumbscrews which i find you can get sufficiently tight by hand, but they also have allen sockets if you want to tighten the holy hell out of them. If you're planning to use this on just one camera, i would say tighten it up with the allen key once you've got it perfect. If you plan to swap i between cameras often, i'd ditch the allen key. My first quick setup resulted in a less than perfect square, but i found you just need to give some closer attention to the two height adjustment screws to ensure you get it lined up nicely.
You get a flip up for quick shaded viewing of the lcd, as well as the base plate itself is similar to a manfrotto 501 plate. I found it does lock into a 501 QR base, but with the caveat that the safety catch doesn't catch and the rear of the VF bracket prevents it from going too far. That said, it does lock into place just fine. Another release is that long knob, which loosens/tightens the flat plate which allows you to quickly mount/dismount the whole VF from the camera, but leave the QR plate for quick re-attaching.
The optics are nice quality, everything looks crisp and clear. I didn't notice there is a bit of pincushion distortion, but overall it didn't bother me. The eyecup is nice and big, though with my particular head, it doesn't quite fit well and i cannot get close enough to view the screen corner to corner. Removing the eyecup was a great quick remedy, but even better was attaching a small chamois which had, which replace the eyecup nicely and allows me corner to corner visibility. If the standard eyecup works for you, it can be flipped for left or right eye'd shooters. The diopter has a nice range, though the turning of it is a bit clunky(not a big deal) as well as it has a marking guide so you can find your perfect spot and if you accidentally knock it around, use the marking guide to get it back into place instead of hunting the optics.
The bottom clip release to flip up the eyecup is a bit awkward at first, since you naturally would brace a finger directly above, but doing so prevents you from actually opening it, so you need to remember to brace your finger(s) on the cup side of the hinge while pressing the button. sounds complicated but it's really not, just a quirk.
You may not think of it, but having a VF on your camera puts it at risk of burning your LCD if the sun catches the eyepiece just right. This VF has a little shutter you ca flick into place, preventing this.
I also own the hoodeye/perfect/GCS viewfinder which hovers around $60, and it's great for what it is, but its much more basic by compassion. On the other end of the spectrum you have units like the Zacuto Pro unit which hover around the $400 mark and give you even better quality overall. The VF4+ sits in a nice position, and i think is one of the overall better values for your money. There is also the same brand model QV-1 which is under $100 and shares a lot of functionality with the VF4+ and may be an even better value if it works for your particular camera. The QV-1 is fairly adjustable, but not nearly as adjustable as the VF4+, which is why the latter is labeled as "universal". The QV-1 also requires an allen key for adjustment, where the VF4+ has thumbscrews.
If you're in the market for a viewfinder, i'd give this one a strong look. There are many options out there, and this one packs in a lot of features, giving it a solid ratio of price to performance/features/quality. If you live near a pro camera shop or rental house, it's always great to get hands on with several units before making a buy. And as always, seek out more opinions other than my own ;)