A personal experience for what it's worth:
My hard drive was failing. I brought the computer and my EHD to an Apple repair facility. I paid an additional amount (probably about $100US) and they restored the computer to the way it was when I left it off. They were able to extract everything from the old HD and didn't even have to use the EHD. The only thing I had to do was download my printer driver.
For me it was worth the extra cost.
I decided to do this. Getting a brand new drive put in!
Mine is already in for servicing for the HD replacement.
I bought this iMac a year ago from a good Mac reseller.
I just found out from the Apple Tech yesterday that I still have a little AppleCare time left. So, if something goes amiss, I am covered. I am having the entire iMac looked over and if anything fails diagnostics, I am having it replaced.
Wish me luck!
Tried to run one last Time Machine backup before bringing it in today...got a "cleaning up time machine" progress bar and then a "drive is full message".
So I wiped the Time Machine drive and restarted the backup. Took eight hours, so it looks like I'm going in tomorrow instead.
Doing a Time Machine backup to two separate drives just to be safe, in addition to the cloner.