Short takes.
I own a 722 since several years. Together with a stereo mic or a pair of omnis it is what comes with me on smaller recordings. On larger recordings, I have a rack on wheels with heavy high end stuff.
As witnessed by others, the 7xx is solid and keeps on working in quite severe surroundings. It is not totally water proof though, for that you need to go to the Cantar
http://www.aaton.com/products/sound/cantar/index.phpComparing the 7xx vs the MR1000 there are some differences in features as well as that ruggedness factor. One worth noting is that the 7xx allows you to listen to an MS recording decoded into normal stereo which to me is an important factor.
I have recently run my 722 flat on against an MR1000. I did two tests, both with MKH20 omnis going Y-cable into both machines. One test with external preamp, DAV BG2, and the other direct into preamps of the boxes. I recorded a largish symphony orchestra, 65 players, playing russian music with lots of dynamics. The MR1000 running at top speed, 5.6 GHz, and the 722 running at 96kHz/24 bit. Once at home the MR1000 file was converted with the included application into 96/24.
The result was interesting to say the least. With external preamp I could hear absolutely no difference. None whatsoever.
Using internal preamps, there was a very slight difference. Not much to talk about, and I could not really say which sounded better.
Now, this is a limited test of the sound, but to me it shows that the difference in sound between units at this level is simply too small to really take into account. One might be better than the other, but other things like moving the mics half a meter makes much larger difference. And selecting the correct mic setup, as example omni mics vs ORTF, makes a difference totally hiding the difference due to different recording equipment.
Well, all this is my opinions based on personal experience.
Gunnar