A minor detail: in terms of the human ability to detect latency it is often as low as 10 ms although it does depend a bit on what you're doing. Perhaps for some 100 ms is acceptable but in many situations I can "feel" latencies of the order of 20 ms. I know several professional keyboard players who need to go to 10 ms or below before things "feel" right. Certainly for me a system latency of 100 ms is far too large.
In some cases latency compensation (as implemented in Ardour for example) can help out. In others (such as running incoming audio through realtime effects for live work) there is no getting around the need to lower system latency as much as possible. In this latter case the target latency needs to be somewhat lower than 100 ms - probably closer to 10 ms or there abouts.
For those working with low system latencies (of the order of 10 ms) the chances of audio skips and other related problems are *much* higher than they are for those who are able to work with higher latencies.