I'm on a JV/XP mailing list and own an XP80 (ROM 1.07)myself. Personally, I have never encountered a prob with the sequencer and some of my arrangements(incl. orchestral) get pretty complicated. I do know that when I
record and I switch track/parts while recording, that will cause the drum track to be thrown off time. I need to stop recording, switch track/part and then start again. This is not inconvenient.

It has been speculated on the mailinglist that too many midi messages being sent at once will clog and cause probs. This would be a prob with most onboard sequencers. A way to get around it is to go into micro edit mode and adjust values so they aren't all played at the same time. There are also alot of internal keyboard settings that could cause probs. All you need to do is find them and reset the values.

I'm far from an authority on this stuff but I feel comfortable saying this is not a large issue. Thousands of users on the mailing list would have addressed this if it were a big problem and the XP80 wouldn't be one of the best selling keyboards. Besides, what else are you gonna buy? An EX5?