I'm looking forward to spending time with the new Gratical viewfinder from Zacuto, which appears to have several things going for it:
1) It uses an OLED screen that's apparently a beauty to behold, with great dynamic range, color depth and very crisp resolution (1280x720p), so pulling focus should never be an issue.
2) Its viewfinder image in isn't overly large, so your eye doesn't have to scan back and forth to register what's in the corners of the frame. That's something that's personally real appealing.
3) It's fairly power-efficient, running all day on a small Canon LP-E6 battery.
4) It has 4 easy-to-reach function buttons, which let you turn on features like a waveform, focus-in-red, magnification, audio meters, false color, etc.
5) It actually has its own LUT system, so you can compensate when you're shooting in various LOG modes.
6) It works with both HDMI and SDI connections, and can pass the video signal from one through another.
That all sounds great -- the only catch is, the Gratical is $3100! But if it works well, it could make sense as a long-term investment that you can use with any camera you own or rent.
I'll be trying it out over the next couple of weeks, and doing a review in Pro Video Coalition in April.
By the way, here's one more pic showing the Gratical side-by-side with the popular viewfinder from Alphatron. The Gratical is taller, but thinner, which seems to be a better balance when you're mounting it on a shoulder rig. We'll see.