... I was thinking of switching it up and getting the DNN991HD...
I have the 990. I hear the 991 boots up faster... but not by much, maybe 10% at best. I have to wait over a minute (it varies, could be longer) after power up for the unit to be usable. I have a remote starter installed in my car. I'll start car in advance to heat/cool the car beforehand, but there are times when I'll just remote start so the HU is already usable when I get in the car.
Another major issue is the navi loses its memory of where you've been, where you want to go, even Home... not frequent but losing it to begin with is too often... always a PITA.
There'll also be times when I'm driving down the road and it'll decide to do a reset all on its own (a reset usually takes ten to fifteen minutes to complete). Fortunately I learned the best thing to do is just power the unit off and back on usually returns it to 'normal' operation. Another infrequent occurrence, but as always another PITA.
No lossless audio file support (makes me appreciate my iPod supporting ALAC).
I like the wifi connectivity a plus... but I don't use it very much... can't use driving down the road and be a safe driver at the same time... but I suppose it'd be okay for something like iHeart radio which requires very little attention (lossy quality sucks though
)
Not ready to replace it with a NEX because of the features it does do good... but can't say much more than that.