I have the iPhone 5, and though the GPS on it is very good, I felt that I couldn't use the phone for other tasks and GPS at the same time that well. If others here feel differently, I'd like to hear how you manage it.
Anyway, just installed the unit on a Universal Vent Mount from Bracketron and gave it quick test. The 1605TM (TM for lifetime traffic and map updates) has a 6" WVGA 800 x 480 display that is very nice and crisp for this size, though, of course, if you've become used to the retina display on the iPhone, (1136x640), it might seem a bit of a downgrade!
Also, I'm not sure but think all TomTom units (and Garmins) besides this one have the much lower resolution 480 x 272 display which looks pretty bad.
I use the British female voice, and found the directions and turn by turn (distances in yards) to be very accurate on my trip. At the exact moment when reading a particularly confusing set of 6 overhead signs at night, in the rain, on the BQE, the voice guidance perfectly directed and read out the exit to take.
The menu system seem OK so far with only a little time using it, but there was one thing that seemed problematic. I like to have the list of driving instructions displayed so that I can always see what the next two or three turns are coming up.
On this unit, as you navigate through the list and reach the bottom of the (I think five) displayed directions, it does not automatically scroll down to the next set of five. In other words, you may be coming up to the fifth turn, but are unable to see the sixth turn or anything after that until you manually scroll down. Yet the previous four directions are still displayed which seemed totally useless.
The mount:
The universal mount from TomTom says that it is not compatible with this model, but it looks exactly the same and it's cheaper (on sale now) so I may return this one and switch if for the TomTom.
I did order the TomTom dash mount, but think that it is too far away to be practical.... and haven't tried the window mount which comes with it for the same reason. Anyway, thanks for reading, and let me know if you have any questions!
Installed in the car:
from above
from the driver's seat: