Well I have had riders for many years and used them both on bike and in the car, never had an issue apart from route planning / itinerary malarkey which is easy enough to work round. Never liked Garmins due to being in my opinion too complicated and on every single occasion both uk and Europe I have been with someone using one it sent us round the rekin where the TT has been faultless.
Bought the 400 last month and thought I had bought a Garmin by mistake, it even looks like a Garmin FFS, the firmware is from one of their car units, its lost loads of the previous Riders functionality and has become over complex.
Some of the stuff I don't like:
If you don't set a destination it stays zoomed out so far its useless and does not warn when approaching cameras
When its turned on it takes an eternity to load up (opposite of TT's claims)
The mount is shite and why did they have to change it the portrait/landscape malarkey is a gimmick and not worth the grief of changing the mount.
The previous mount could be bolted directly onto a mount a la Triumph / Kawasaki where this one has to have a ram ball attached to the mount then a ram arm then the mount which is highly nickable compared to the screwed on predecessor
When the mount does not have the power cable attached you are left with an annoying lead flapping about and no plug is supplied to stop water ingress, the previous Rider had a tidy recessed socket when not powered.
The plug is very small and fragile looking too.
Tried the thrilling ride thing once so far and had to give up after 5 mile as the roads were shite and unless you were on a trailly or "adventure" bike your bike would have been shagged after negotiating all the gravel / potholes / farm debris etc we encountered (others on pure road bikes) not TT fault but non the less.
Not impressed and even after a rushed update still work in progress as far as I am concerned and I have told them too on their forum