As we learned in the thread "Unison strumming why??? Help please!!! (edit: previously thought to be Hypersaw)" it seems that unison mode not only randomly shifts detune, panorama, and LFOs, but also the filter and amp envelopes.
This leads to sporadic lag of notes, especially with chords where it is perceived as "strum" or untight timing. If unison mode is switched of, the strum is gone, if you add more voices in unison mode the strum is stronger. Whether this is a bug or a feature is hard to tell, but it's interesting and different from the unison mode of other VA synths. However, it ruins the usefulness of unison for certain types of sounds which require exact timing, such as pluck, arp and bass sounds.
Therefore, it would be nice if it was possible to control the "tightness" of the unison.