well, my main concern with time machine is 2 issues. first, when your time machine drive fills up it throws away the oldest files to make room. if you know this is going to happen that's no big deal, but i've had friends that were using TM for archives/backups and this bit them. second, when i've used TM in the past, everything on the TM all the info on the drive is a giant .spars bundle. you can't access the data without TM. what if i need a backup and i only have access to a windows machine?
Hmm, see neither of these two issues effect me at all.
There is enough space on my main Time Machine backup drive that I just looked and I have yet to have a backup deleted (also when this happens I my preferences set so that I will be notified). They go back to January 2013 which is WAY longer than I need. Truth be told I really only need the latest backup but I guess it's nice to be able to go "back in time" so to speak if a file is accidentally deleted.
Also, the info on my Time Machine drives is not a giant .spars bundle and I do not need the Time Machine application to access it. Not sure what you are referring to. Perhaps older versions of Time Machine behaved that way? On my Time Machine drive the data can be accessed through the hard drive itself, just like the internal drives it's backing up. For example when I open a backup folder on my Time Machine drive through Finder I see two folders, one labeled "OSX" the other labeled "DATA1", these are the names of the internal hard drives I have Time Machine set to backup. I can then access the data in these folders exactly as I can access them on the internal drives. No need at all to use the Time Machine application. I can play audio files, open documents, drag data back to internal drives, etc.
Anyway, Time Machine has been working just fine for me and my system. I have been using it for nearly 2 years without a single real world issue. Perhaps I'll look into using SuperDuper! again, although I'm not really sure I buy some of these claims that Time Machine is some awful unreliable backup method. Seems about as good as any other to me. Certainly better than just storing data on one hard drive or backing up to DVD or whatever. Maybe not as robust as say dual carbon clones but I've verified time and time again that after I perform a Time Machine backup all the data is indeed backed up and easily retrievable.