From what I have heard, OS DACs do need jitter control, because the digital filter introduces phase instabilities.
Jitter comes from the digital interface connection between transport and your DAC. It is a universal problem that affects all DAC's, DSP's etc. It is unavoidable. Some DAC's use techniques to decouple the clock signal coming across on the digital interface => this can completely remove interface jitter in a good implementation such as the DAC1. (Of course the clock in the DAC itself will have some jitter itself - there is no "perfect" clock - however this internal jitter should be orders of magnitude less than what you get from any digital interface)
Phase issues occur when using brick wall filters in non-OS DAC's. The idea of an OS type DAC is to avoid the use of steep brick wall filters and the phase errors they inherently bring into the audible range.
Some people will prefer a more jittery sound - it will give more harshness and edge to the music and can help make laid back equipment sound more dynamic, exciting and revealing. (Remember that modern CD's are mostly hyper compressed to give a harsh edgy sound and some people prefer this - jitter is similar in the way it can affect the HF)
