Which speakers did you find bright, fatiguing or just disappointing in some way?

I'm in the camp that the KEF LS50 is way over rated for the price. I have a pair of Ascend Acoustics CBM-170 that sound almost as good for a third of the price.

Years ago I had a pair of Walsh Ohm towers that sure never did it for me and were expensive as heck. Same with a pair of Dynaudio Contour 5.4. Almost 10K and virtually no bass.

I have a pair of used NHT bookshelf in the garage and they sound great for what they are and cost. Had a pair of PMC TB2 out there that were awesome and wished I'd kept.
Like other have stated, have heard several B&W's and Monitor Audio's in high end shops and thought they all sounded decent but way to bright and would be so fatiguing in no time.

B&W 8 series ---Just plain plain and boring sounding.
Piega Master Line Source 2 --- I so wanted to buy them and then I heard them...ughhh just terrible
Magico S3&5 ---- they were just to bright and in your face.  I know I would have gotten tired of them quickly even though they are considered a high end speaker.

I will stick with my Viking Acoustic Grande Voix Dual Horn speakers everyday of the week. 

KEF R3
I wanted to love them! They looked and sounded great at the big ol’ Magnolia Audio showroom, and I assumed that if they sounded good there, they’d sound GREAT with real gear (vinyl, tubes) at my house.
But there was something happening around 3Khz that made my ears ring. Some things sounded really alive and exciting, but there was always that sharp upper mid spike clobbering me and forcing me to turn the music down. After a couple of weeks of break-in (pink noise, dynamic music, etc.), I finally gave up and returned them.

2nd Prize: B&W 685 S2
These guys got such universal praise that I HAD to check them out. To be fair, they sounded more full-range than I’d expected (even subjectively deeper and more dynamic bass than my previous Nautilus 805s). Definitely a detailed speaker. But as their manual described,

"where there may be a significant increase in the amount of detail compared with wha tthe listener has previously been used to; the sound may at firstappear too "up front" and perhaps a little hard"

... yes. When the MANUAL tells you this, maybe it’s a sign?It went on to recommend a break-in period of anywhere from 15 hours to a month "or longer." After 3 days, I couldn’t hack it anymore.