I think our neck of the woods is not as bad as the southern half of the Highlands. Kevin had a week off last week (well timed by pure coincidence) so we visited a few hills. My thoughts on how busy it was:
Inchnadamph car park - several cars parked there in the morning but it was quiet on the hills. We were doing an obscure route on Glass Bheinn so didn't meet a single soul.
Mullardoch Dam car park - quite busy considering it was mid-week. I counted 9 other cars when we arrived and we took the last parking spot
Again, we were climbing a less frequented ridge, so the only people we saw were on the summit of Sgurr na Lapaich.
Morvich NTS car park - a few cars but there was still room for us when we arrived. I counted four other walkers and two cyclists on the paths below Beinn Fhada/A'Ghlass Bheinn. So it was very quiet for a summer Sunday.
Glenmore Lodge car park - still plenty of space to park at 8:30 in the morning and a quiet walk-in to Bynack More, but on the way back it was really busy, lots of people near the Green Loch.
The rest of our routes were too obscure to be busy... So I think these days, if you want silence and solitude, pick an unusual approach to an unpopular hill