I too am having the touch screen going crazy syndrome.
I can't complain to much because I have had this 550 for about 4 years now!.
I'm torn on doing the flat $150 refurbished swap or replacing the touch screen. http://www8.garmin.com/support/outofwarranty.html
Does anyone know if you buy the refurb model will Garmin transfer the lifetime map upgrades over to it? This for me is going to be the determining factor. By the way the refurb now has a 90 day warranty.
As for the digitizer screen, so this is the guy to buy from for the correct size: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190417956530&ssPageName=ADME:X:RTQ:US:1123
Did the screen have the necessary adhesives on it to mount it to the frame? If not what should you use? Any one know how long it would take to get this part to the US?