I have had one for about 10 months.
Positives:
Lovely big screen - OS maps look great and it's a delight to just scroll around exploring.
Bright colours on screen.
Very handy to be able to switch to display current way up, so a left turn on the map will appear on your left.
I can get around 10 hours battery life on the built in battery if the screen's on all the time.
If the battery runs flat, it does save the data, so once you restore power, nothing's been lost.
If the battery runs flat, you can run on 3 x AA.
You can import anything you like as a .jpg to view on the screen, such as train timetables, pictures of your destination, notes etc.
Loads of memory to store all your regular routes and just load them up if you change your mind.
Button's and joystick very easy to use.
Easy to switch and display the profile if you want to know exactly how steep the last hill was (or the next one coming up).
New area maps can be easily added on the SD card.
Very easy to add on warning areas to highlight things.
The unit is very secure on the bike mount and easily removable.
Downsides:
If the screen brightness is set at 80% or higher, it can interfere with the signal to wireless cycle computers, so they stop working.
In bright sunlight, even with the filter set to enhance features, it can be difficult to spot your track.
Sound is useless. Even on the loudest setting, you can barely hear the beep in a quiet room.
It may be just me, but if you wanted an audax instruction like "SO at X" to show up as a waypoint instruction, they have to be manually added.
Waterproofing concerns on the basic unit.
Once the battery starts running low, although the battery display turns red, as it's in the top right hand corner, you can miss it.
I had to complain to get them to update the base map on my unit, as this was 4 years out of date.
The add-on maps are expensive.
It can take a few minutes to get a lock especially if you've switched it on some way from where it was last used.
It can't do auto-routing like some Garmins. If you go off track, all it displays is a line pointing to wherever your end destination is.