I generally tend to end up at between SFC and 2500 feet.
However, a couple of years back I ventured out on a beautiful clear blue sky day over North Wales, in the vicinity of Snowdon. Anyway, Snowdon looked huge so I decided to get a bit higher. I ended up at 6000 feet and suddenly I was overcome by the feeling that something was very wrong. It felt like I was stationary. I checked the ASI, 100 knots was showing. The rev counter was registering revs (as it would!) and a scan of the other instruments and my GPS appeared to suggest that all was well. But the feeling was still there.
Obviously it was because I wasn't used to being so high, but it did rattle me for a while !