After watching the availability for many months while searching for a unit with a brighter screen, I bit the bullet and recently bought a factory-refurb 590LM from GPS City for $595 and have been happy with it. My previous unit was a 660LM and it worked fine but it was nearly impossible for me to read under certain daylight conditions and the 590LM works much better in daylight, plus the lettering at the top of the screen is much larger so another +++ for readability in bright daylight. Someone with younger eyes may not have that same problem.
Truth be known, the 590LM's brighter screen still falls short of the Zumo 550 in the brightest screen competition - at least for me - but those units are ancient now.
Below is a simple locking mount I made for my 660LM and also did the same for my new 590LM. I saw something similar on a Garmin forum several years ago so borrowed that idea to make this simple locking plate. It was a lot cheaper than buying a Touratech locking mount!