I have a TomTom Rider 1 and LOVE it.
Great clarity on the screen in bright sunlight, can be user-set to auto dim at night as well.
Comes with a Bluetooth and 2 earpieces. One is a simple earbud, and the other is a speaker and mic that you can velcro in and out of a helmet. I leave this in my Shoei, and if I wear another helmet I just use the earbud. Loud enough for me with my RPW pipes blasting too.
I bought mine off of eBay from a seller called zkarlo, they have a very unique mounting setup that comes with it, so mine mounts front and center between my risers, or can be mounted on the bars by the grip if I wanted. I paid $180 for it, then had to buy the Bluetooth separate from zkarlo (they had none at first) and that cost me just under $100.
It's small & portable, so I can take it from one bike to my other easily. No external speaker, so it is weather resistant, no worries about downpours.