I never know how I'm going to feel and that's the fun of it. Sometimes I can be seriously underwhelmed - Lacra stone circles, the first time at Mitchells Fold, Blakely Raise. . . even Callanish! That's not to say I didn't enjoy my visit or wish I hadn't gone, it's just the arrival didn't have the 'wow'.
Yet sometmes I get a buzz like no other, almost to the point where it's scary. Cothiemuir Wood and Tyrebagger in Aberdeenshire, the Druid's Circle by Conway bay, Boscawen Un and Reenascreena in Cork all completely moved me in a way I can't describe.
I'm hoping to get similar vibes in Dartmoor soon. I bought OS map 191 two days ago and I can't believe the amount of sites there!
I always love the feel of Boskednan and Tregeseal circles, Boscawen-Un depends on whether its busy, Merry Maidens depends on how many cars are parked up, because you see the cars first - sometimes there's a lift if there are cars but the circle is empty!
The Brecon Beacons sites are usually accompanied by a mega sense of achievement but sometimes are less atmospheric if they're busy. Actually, the feeling of arriving at any site is always much better if there's no-one else there.
Each time I've visited West Tump longbarrow I've been overwhelmed by a sense of peace and once by the sense that there was a real presence at the site.
Recent "wows" definitely include the Dartmoor rows and cairn circles I've been to (Stalldown, Butterdon, Kiss-in-the-Ring, Drizzlecombe, Down Tor, Ringmoor, etc) which have really impressed.
The only real disappointments are where there's no access (or if I really run out of time and have to miss sites). Rain doesn't affect - Ringmoor and Brisworthy, Avebury and Nine Stone Closes have all been recently visited in pouring rain and I loved all of them.
[By the way, you might want to get an OL28 too. :-)]