There are quite a few of both of these for me.
Pleasant:
1. Expedition Everest (DAK) First time I had ever been on it was just a few months ago and it was so smooth, so fast and really a lot of fun.
2. Cheetah Hunt (BGT) First time on it was this year's Howloscream and go tthe front seat and WHAM! Right from the get go, this ride was awesome. Had a permanent smile on my face the whole time and for a bit after the ride.
3. Harry Potter (IoA) Incredible theming, details and overall experience.
4. Soarin (EPCOT) Awesome overall ride.
5. "Rehabbed" Big Thunder Mountain (WDW MK) First time in 5 years since I'd been on this and this time was at night, in the back and it was awesome! Love this ride.
6. Rip, Ride, Rockit (USF) Wasn't sure what to expect with this ride but it was pretty impressive. First drop was nice and intense with no slowing down over that hump.
7. Dare Devil Dive Coaster (SFoG) Fun, fast and smooth and intense in some parts. Excellent.
8. Manta (SWO) First "Flying" coaster I had been on and it was awesome.
9. Goliath (SFoG) - Awesome smooth ride that was fast and intense. Loved the speeds and G's!
Unpleasant:
1. Great American Scream Machine (SFoG) Very, very rough and hard. Needs something done to restore this once great ride.
2. Superman (SFoG) Nice start but it quickly fades out after that.
3. Star Tours 2 (DHS) I guess I'm a traditionalist here cuz I think this new version just tries to do too much with all the "accidents and mishaps" that happen in Star Wars. Just seems like the whole ride is based on special effects and not much of a real story behind it.
4. Monster Plantation (SFoG) Was expecting that with the new rework and the advance in technology that this ride would be better than it is. I was not impressed with it.
5. Haunted Mansion Cemetary (WDW MK) While this is my favorite attraction of all time, I think this "extra" walk through was unneeded and a waste of money and space. Are we, as guests, too short in attention span that we need something to do at all times? Can't we just wait and anticpate the attraction? I love most of the changes inside, except the bride in the attic, and always look forward to riding it. However, I skip the cemetary line.