I saw one of these in Halfords the other day and, as I had been thinking about getting a dashcam for a while, decided to go ahead and get one. It's my first dashcam so I don't have any basis for comparison. First impressions, however, are generally favourable with a couple of reservations which I'll get to in a moment.
First, the positive. It's a good-looking piece of kit which attaches quickly and easily to the rear-view mirror by means of small suction cups. I also elected to fit the 'optional' stretchy rubber straps which loop around the mirror for added security. The hooks for these look a bit clunky before fitting but once in place they're quite unobtrusive. The whole thing can be removed, re-adjusted and replaced in a couple of minutes, but it's clearly meant to be left in place all the time. Because the camera lens sits well back from the windscreen (see below) it's quite difficult to spot from outside the car, so it's not immediately obvious that you have a dashcam at all. I went for the Halfords £30 fitting service which seems fair value considering that it includes a Nextbase hard-wiring kit which they also sell separately for £20. The guy made a very neat job of the wiring and the only difficulty was fitting the piggy-back fuse holder into the fuse panel (a criticism of the awful fuse panel placement on my Peugeot 308 and not the fault of the hard-wiring kit). A row of buttons along the bottom edge controls all the functions including a setup menu on the display screen which appears in the left-hand quarter of the mirror. The screen remains on all the time by default but can be turned off automatically (described as a screen-saver) or directly by one of the buttons (my preference). The display screen can also be replaced by a digital readout of the speed from GPS, but I find this distracting. I was a bit worried about the size of the mirror which is about 25% wider than the car's mirror. In practice this isn't a problem once you get used to seeing the tops of your own and your passenger's heads at the same time. The reflective surface isn't quite such good quality as the car's mirror and there's some very minor distortion but overall it's perfectly adequate and I don't have any complaints. The camera starts up and shuts down with the ignition and once it's set up you don't need to touch it although start/stop recording, screen on/off and mic mute can all be performed from dedicated buttons. The Micro SD card is easily accessible on the bottom edge. Picture quality looks pretty good to me, although there's noticeable barrelling around the edges. Internal sounds record well and indicator clicking can be clearly heard on the recording. I assume the software is pretty much the same as other Nextbase cameras, so most people here will be more familiar than me. There's a wifi function which allows files to be transferred to a phone or tablet, for example, but it's a pretty slow transfer and I'm finding it easier just to plug the SD card directly into my computer.
I do have a couple of reservations about the Mirror DashCam and the most important one is about its fundamental design. Because the mirror is angled towards the driver, in a RHD vehicle this means that the camera lens which sits on the left side of the mirror is set back from the windscreen (in my car at least) by a significant amount and unless adjusted would point pretty much towards the nearside. To make the camera point straight ahead with my seat configuration requires swiveling the lens to the extreme of its travel. If my seat were just a couple of notches nearer the steering wheel, thus increasing the mirror angle, I think it might be difficult to make the lens point straight ahead at all. Obviously this issue will vary according to the relative angles between the driver's seat and the rear-view mirror, and may not be a problem at all for a LHD vehicle but it is something to consider before you buy (which I didn't!). The other disadvantage of having a camera integral with the mirror is that it inevitably lines up with the mirror mounting which in my car comprises a large black box containing all the clever windscreen-related electrical gubbins you should never leave home without. This box produces a substantial and very obtrusive blind spot on the video which simply can't be avoided (see attached screenshot).
The only other negative observation so far is that the date/time stamp on video files seems to be a bit erratic, especially when starting up and before the GPS kicks in. One effect of this is that journey segments don't always play in the correct order when loaded into Replay3. I'm not sure yet whether this is because of something I'm doing wrong or if it's by design but from some of the comments in other threads I'm beginning to think it might be the latter...
In summary: Do I like the Mirror DashCam? - yes; Does it have a couple of annoyances that I should have thought about but didn't? - yes; Would I buy it again? - based on the experience so far, probably.