Ancient thread, I know - but as this is a forever needed function I am adding info here from my own experiences in the years since the OP.

To resume here I must 1st mention that the best of what I've found & used taught me to stick with EXT3 as an important part of the process (and frankly I've seen nothing that has made me change that choice...).

2 backup options have served me well most of the time between my additions here:
A - Systemback
B - Macrium Reflect

Details pertinent to the above:
Systemback required some digging & learnings both to get it up & running on Ubuntu Mate 18.04 - and to learn its foibles.

That having been done, it is amazingly excellent for cloning an entire system & I've used it for that many times already with 100% success.
Its single limitation is that for backups over 4GB it will not make an ISO, so those must be written to a USB stick - which is great anyhow as it makes a terrifically usable boot media that does both live and installable sessions.

Reflect is ONLY used via boot media as it is winpe3, but it does handle up to EXT3 for me without fail - with the only possible problem afterwards of sometimes needing to also use Boot Repair Disk to correct GRUB2.
(It also takes WAY longer to boot up than just using the already installed Systemback...)

Very important to mention here is the reincarnation of ReDo !!
I have gotten it & made a boot media from it, but have yet to test & verify it for myself - so, it is definitely very happy news for it to be back, but please also remember - YMMV.

Back when I posted the above answer I did truly adore ReDo Backup, it was so easy & simple & it just worked.
Then, after the days of Ubuntu 12.04 it was abandoned.

Now, at long last it has been brought back from the dead - YAY !!!

For anyone interested, have a look at these pages:

Home page=>
https://github.com/rescuezilla/rescuezilla

FAQ=>
https://rescuezilla.com/help.html

Limitations=>
https://github.com/rescuezilla/rescuezilla/wiki/Rescuezilla-Limitations

Release =>
https://github.com/rescuezilla/rescuezilla/releases/download/1.0.5.1/redobackup-livecd-1.0.5.1.iso
(From https://github.com/rescuezilla/rescuezilla/releases )

My own cloning process goes this way:
I have taken my time to create a tweaked up version of 18.04.3, backed it up with Systemback - and transferred it with 100% success to a bunch of desktop as well as notebook PCs with various h/w.

Some were 100% new & just built (bare metal...), some were bought bearing the abortion called '10' which was sanitized away 1st (without ever even getting booted up to it), and the cloned system has been dropped into older h/w as well - and just works.

Please bear in mind that my solution INCLUDES the home partition which has NOT been used to store any personal data before the cloning process so that all settings in there are reproduced - which makes the outcome arrive as a system that takes very little time to finish setting up per-user.

I hope all of this added info will be helpful for other folks here !!