RASPUTINSREVENGERELOADET  Very easy to setup and run.

After a long search for that kind of software (Mozy, Wuala, Dropbox and many others), finally I discovered Arq! There is really nothing to complain about this software, so I give it 5 stars.

It fulfills all my wishes of backing up online (security, user friendliness, price, CPU usage, configurations and so on ) ...

Thank you developer!  
(Version 1.5.13)

BIGBOYSDAD  Hopefully, if the worst happened and your Mac disappeared, you'd be able to rely on your cloned backup (which you do everyday right?), restore it to your new Mac and be up and running. So, in these circumstances, what would happen with the Arq backups from the previous Mac in terms of syncing them with the new Mac? Its a question I asked the developer and within minutes, he came back with the answer I was hoping for - that, in this situation, the restored Mac can sync with your previous online backups straight away. No reloading your data all over again for weeks/ months on end just because you have a new Mac - another example of how this is superior software.  
(Version 1.5.13)

BIGBOYSDAD  If you try most of the online backup services, it will become apparent that the best top two applications are this one and Backblaze.

Both are simple to operate, work efficiently in the background, appear faster than the alternatives, enable archiving of changed/ deleted files and do not hog system resources. Both developers are very quick to respond to enquiries too. It’s after this that Arq begins to leave Backblaze behind, producing copied file metadata identical to that which has been backed up, more flexibility with archiving and the knowledge that your backups are kept more securely and redundantly with Amazon amongst many facilities, not primarily in just one central storage premises (luckily, the Backblaze technicians were smart enough to ensure there was no data lost after their power outage in April this year).

If you are backing up, say 70/80g of mostly photos, music and documents like me, the difference in monthly cost will be $2 to $3 dearer with Arq, but that’s the difference between a very good product and the best. In summary, Arq, used in conjunction with your favoured local backup/ cloning tool is currently the best quality backup there is.  
(Version 1.5.13)

MARUKO DRINKING TEAM  Completely awesome. This is the correct way to back up data on the Mac. The only reason to use something else is if you can't afford to back up to Amazon S3. In which case, well, you;ll have to spend a lot more time dealing with your backup system, no matter what software you use.

As an aside, I once restored my home directory using CrashPLAN. It took TWO DAYS to restore my 60GB home dir, even though the backup storage was on my gigabit LAN. When it was done, thousands of modification dates had been reset to the current date, and other file metadata was lost. Arq is MUCH faster, even restoring from Amazon, and it is one of the only Mac backup apps that does not subtly corrupt your files by losing metadata and dates.  
(Version 1.5.7)

RUSSFAM  I would agree with the comments made previously. The software is first rate, easy to use and does what it says on the website. Speaking of which i would recommend to people to visit the developers website. The detail which they have gone into to ensure that their backup software is effective is incredible, it is not just hype because they publish their methodology so ( if needed their tests could be reproducible).

Also, i ran into a few problems whist restoring a large batch of photos ( > 1gb ), Arq crashed on several occasions. But was able to restore my files by downloading in smaller batches (about 250mb). After each crash, Arq displayed a pop-up asking if i wanted to send a report. which i duly did. What i am finally getting around to saying, is that one day later a fix is published. Now that is what i call service. My faith in the software is rapidly increasing.

Thank you for saving my butt, if i had lost the wife's pictures.........!!  
(Version 1.5.7)

NULLSET  Wow, that's service ... Amazon announced Reduced Redundancy Storage on Wednesday, and the next day Arq has been updated to support it. Gotta love those dedicated developers :)  
(Version 1.4)

DAIYI  I concur with the previous reviewers. In my experience, Arq has been the best backup solution for me in terms of ease of use, intuitive interface, and reliability. I had been looking at other possible solutions for backing up to Amazon S3 servers and Arq was by far the finest for my needs and preferences.

Although there isn't much to do to get up and running, Arq does allow users to set preferences accordingly. For example, network preferences can be set to "maximum," "automatic," or "fixed (by user)" transfer rates.

Another great feature included in Arq is a "Budget" setting, which ensures you don't go over a monthly rate for storage (not bandwidth, however, which is free until June 2010). Just enter your monthly budget and Arq will indicate how many gigs you'll be able to store at that price.

As the developer Stefan points out, Arq is like Time Machine for remote backups. That's an apt analogy and an efficient way of doing backups of your most important files.

Although the price point is slightly higher than other products out there, the product is top notch and using AWS you'll end up saving money on storage over time. Highly recommended.   
(Version 1.3.15)

IRRADIATED SOFTWARE  I've been VERY pleased with Arq. I needed a solution that worked with S3, and Jungle Disk just didn't cut it. Arq has a very streamlined interface and really nails the "set it and forget it" requirement.

Most of all, I'm confident in the backups. I've done a couple restores just to test, and all my meta data made it back. This is a HUGE requirement for me since I still have a lot of AppleScripts and older data files with resource forks, which other backup programs step all over or ignore altogether. Following the developers blog a little big, I can see the care and effort he has put into making Arq a solid backup solution.

While the price is on the high end of the backup solution range, it's still competitive, especially given how care free my use has been so far.  
(Version 1.3.15)

NULLSET  Absolutely terrific software. Backs up flawlessly each time, restoring is easy too. Price is a bit high, but given that there aren't any other automatic S3 backup programs (other than JungleDisk) and given that Arq has such a nice, simple, and easy to use interface I'm inclined to overlook it that minor complaint.  
(Version 1.3.15)