If you have a tracker mortgage, read the small print very carefully before closing the current account. This (rather long) thread explains why.
Having switched personal current a/c a few times in the last few years, I tend not to rely on banks' switching services and prefer to send my own notification to the various parties with whom I have DD arrangements. Maybe I'm overly cautious.
Yes, I did this a few months ago: switched my current account from Dansk to PTSB, and then changed the current to a mortgage servicing account (do NOT close it).