If there is a defining feature in Apple's Leopard, it's Time Machine. As cool as it may be, the fact is that we, as Linux users, are obviously not going to see much benefit from this is pitiful. So it's a good thing that open source developers have taken it upon themselves to create something similar, be it not a 'pretty' alternative.
Going Back With Flyback. A needed GUI alternative to rsnapshot, Flyback provides much of the same functionality, but does so with a nice GUI wrapper to make the entire process more user-friendly. The UI appears to be GTK-based and overall, it's impressive. Just about everything you want from rsnapshot is here for the common man to make the most of it with.
Flyback creates successive backup directories mirroring the files that you want to make sure are backed up. In the truest sense, this has the potential to become a very clean, useful means of backing up a system completely. It can be fully automated and can be run via backup, which would likely meet the needs of the most hardcore command line users.
And Here Comes the Negative Feedback. Criticism is to be expected to some extent, but it is really pointless for people commenting on this project's goals to mention applications that may do something similar, then trail off with "why not use this instead." Some examples that were mentioned include TimeVault (terrible UI, still very much alpha release, but a cool idea) and Simple Backup (totally different goal, but works well with specific folders). What kills me is none of the responders using these examples actually had a point to make or constructive suggestions. There were others that had valid questions and feedback, but it did not take away from the stupidity of pointing the obvious - there are always other options, but some people may want something simple that works.
What's interesting about this application or anything similar is the value of time-based system snapshots. Let's face it, sometimes overwriting existing backups does more harm that good.
Cool 3D Effects Coming? Another thing that will indeed, make this take off sky high with growing user numbers will be to add a little 'gloss' to the mix. Basically, make it 'feel' like Apple's Time Machine. Personally, I would enjoy this if we can not blend in dependency with Beryl/Compiz Fusion or any of the other 3D bling effects that so many beginners have fallen in love with. I will take my Metacity basic windowed environment, thanks. Then again, I'm happy with this working as is, without any special effects. Why eat up any extra resources, right?
Further Considerations for Function Over Appearance. The only advice or input I would give the developers of this rsnapshot-like application is to think like a Linux user. Don't get too caught up into being fancy, use the KISS principle and don't be tempted to make this dependent on anything related to a composited desktop.
People that are serious about Linux, really serious to the degree of not even using Windows or OS X at all don't need glossy features. The UI is excellent, so concentrate on bug fixes and new functionality. But please, if you do decide to take things to OpenGL, at least offer us the original version with the new glossy edition, should it ever come to light.