Just an interim report - I'm pushed for time right now -
The device is very susceptible to handling and wind noise. I thought the day here was pretty still wind-wise until I saw and heard the considerable low frequency rumble which the device recorded unless it was in totally still air. Use of a dead kitten outdoors is mandatory. On the plus side of this, the wind rumble indicates that the mics go down to a good low frequency.
The jury is out on the quality of the built in mics. There's plenty of low frequency extension. There's no roll off at the HF end. But I'm a bit suspicious that in the middle there's some colouration. To pin that down I'll need to do a very careful test in comparison with other recorders I have and with a Sennheiser MKH MS pair (into another recorder) as a reference. They seem to be as low noise as any other such recorder these days - I have no concerns in that respect at this time. Stereo image is good as you would expect from the mic configuration.
(It seems to me that it should be fairly easy for manufacturers to get a good flat response from built in mics, as the response of the capsules is known and the recorder electronics should be designed to compensate for any lack of flatness.)
Every time you plug in the headphones, a box pops up warning you of the risk of hearing damage, and the volume is lowered to a certain level. You can then ignore the warning of course, but it's a bit of a pain during testing when I'm using the same cans on various recorders.
The input level control is a bit fiddly in use, but there is a display not only showing 0 - 90 but also how many dB up or down you have dialled, relative to the starting position before you turned the knob. As the knob is a rotary encoder, small adjustments can be made more easily than with a control which can only rotate through 350 degrees. Apparently this is digitally controlled analog level control.
Otherwise, it's a delight to use, in terms of the menus and transport controls, which fall nicely to hand. Compare and contrast with something like the M10 whose control layout is a bit idiosyncratic - I find myself peering at its buttons and having to think which one to press, especially when using menus, and to see its current settings you have to scroll all the way through all settings. On the DR22 it's all there on one four-tabbed page (and the first tab has most of what you need during a recording).
The remote control Android app is indeed woefully short of features, but it does have metering, time info, and start/stop/pause/play/record/skip. I put the recorder on a table at one end of the house and used the remote at the other end, and it worked fine (if only for the currently implemented features) over a line-of-sight distance which would equate to the distance from a mic stand in front of a band back to the first few rows of an audience. Using the remote even close gets round the problems with handling noise. It also enables simple things like recording yourself talking (and thus not having a clear sight of the controls and display) but being able to operate the device from a phone beside you.
So, the wifi thing opens up the prospect of using the recorder as a stereo mic which would normally need to be cabled back to a recorder, except no cable is required, while retaining full control (once the apps are actually finished). This is great, but if the mics are indifferent, it's not such an attractive scenario. You get what you pay for I guess - the DR44 would enable you to use your own higher grade mics at the top of the stand with the recorder strapped on lower down and remotely operated.
So, watch this space and I'll try to do some valid tests on the mic frequency response. I'll also hope to do some ambience recording with a dead kitten fitted. For further info see the two-part review on YouTube by Max Yuryev who has done a good job, though his mic tests are not the most scientific.