I updated my Nuvi 2545 (& BaseCcamp) 24 hours ago without any problems - I must have checked for updates soon after release! I have not really used it in anger yet though - just checked it displays my local map ok.
Nevertheless just downloaded the whole lot and updated both my nuviCam and PC. Whole process was flawless this time and definitely quick (~10 mins max?).
OK, maybe someone can help me out. My update did not go well, first time ever I got error - update of European maps did not complete, I simply got a red banner indicating error - no information what kind of problem it is. My product - Nuvi 2559. What is annoying from the start the Express tells me my Garmin is not connected - but it is. I have to do a few connect/disconnect before it finally realizes the unit is connected. I also installed the newest version of the Express (as of today). I am using PC Windows 7. I got 40 GB free space on my drive.
EDIT: it finally worked, I switched to anther USB port o my PC.
Off-topic a bit but... I'm glad that you resolved it.
And yes, I was myself plagued by flimsy USB connectivity on my former PC (13-year old Win XP) as well - especially towards its latter days - and I never could quiteget to the bottom of it as it sometimes worked without any issues, sometimes it had tantrums and disconnected / lost sight of satnav unit after moving mere few MB of data. Needless to say it manifested itself only with satnav unit, but never with external USB HDDs - I therefore presume that power consumption might have had something to do with it.