yes and no...
When training for the plank IR I stuffed up an ILS because I cleared my ears as we were turning onto the localiser, screwed up my balance no end.
On the other hand..
Went skydiving with a cold once - 12000 to 2000ft in a minute, all I had to do was clear the ears and it was back to normal.
Probably shouldn't have done it, but it was FREE as HM the Queen was paying so I didn't want to miss out.