I followed this development from the first version and indeed it seems that everything is very smooth.
The real good thing is that background tasks (system tasks) dont interfere with the user environment ('cause they are isolated in another group).
This is achieved by the cfs scheduler that isoletes tasks belonging to the same tty.
There is also the solution proposed by systemd or cgroups (made in user-space) but Linus stated that that would be not the solution
1) user-space is a fragmented mess;
2) user-space daemons are a total mess;
3) the whole "user space is more flexible" is just a lie
Other than that, for what concernes IO bandwith isolation, take a look at what Mike is saying: "Next logical auto-step would be to try to subvert cfq" http://lkml.org/lkml/2010/11/15/155. Perhaps he is joking ;).