I have had to restore a backup once, so I restored the most recent version, which was restoring an old version of the file. I ended up frantically restoring all the different versions of the backups, and one of them was the most recent version. But it was considered an old version by Arq, I'm not sure precisely which one, but it definitely wasn't in the top 3 most recent ones.
And more recently I made a backup to glacier, and it is trapped in "in progress", even though it appears that it may (or may not) be complete.
I haven't used it much, maybe 6 times, and 2 of the times it's had these catastrophic problems I'm talking about. I'm going to switch to another solution. I was considering rclone (like I mentioned) or Crashplan, ironically.
Crashplan worked well for me, sometimes I have to restore a file that I overwrite or that ends up being corrupted because of buggy (in-house) software and I never had any problems with that.
My main issue is that I went with free plan + my own server because transfers to their servers were really bad. But to supply your own storage, you have to install Crashplan on the server, which uses significant amount of RAM. So this rules out backuping to my NAS (not enough memory there, even though it's x86 and technically people ran Java on it).
The other issue is that file format is (AFAIK) closed, and also you an account and connection to Crashplan service, so I'm not completely sure that you really own the data. I didn't do much research here, though.
If you mean client performance in general, I never had problems with that, it's just the connection to the server overseas was not that great. I have my own dedicated server in Europe to which I have much faster connection.
