Add me to the long list of people with Time Machine problems.
I installed a WD 3TB MyBook Live NAS drive and set up Time Machine on my iMac, connecting as guest as recommended (seems a bit insecure to me, but anyway...).
The first backup went perfectly - and that was a large one of about 500Gb. I left it overnight but it was done in the morning. I reckon it was copying at about 12 Mb/Sec which isn't too shabby over WiFi (iMac and WiFi router are in the same room). I was very happy with it's simplicity and the fact I didn't have to go through an ardous setup procedure.
But... As I was doing some video work I turned off Time Machine so it wouldn't interfere. Later I went back to Time Machine and told it to "Backup Now". It went through the prep stages quickly enough (a few minutes) and started backing up. However now the backup absolutely CRAWLS to the point it's not worth doing.
Of note:
* I tried manually copying onto the NAS drive and it worked fine - no delays or slowdown, so it's not my network..
* If I "Enter Time Machine" I get stuck there "in space", cannot do anything and have to Force Quit.
* Spotlight seems to be working OK. I never see it indexing anything but "just in case" I added the TM backup volume to the exclusion (Private) list in System Preferences.
I've given up on Time Machine. All I hope for is that some day I turn on my Mac and it tells me there's a fix to download. Meanwhile, I drag and drop my files manually to the NAS drive...
This thread is now almost 11 months old and over 40 pages long so there's an obvious issue here. APPLE. DO SOMETHING!!!!