I am a total moto slut...I have loved all the bikes I have owned and ridden with just a few exceptions:
2010 Triumph Tiger 1050, had shit fueling, and worse rear shock. Engine felt like it should have been as much fun as a Speed Triple, but never lived up to it. Bars made my hands numb in 15mins of riding. Riding it was.... boring.
My 2007 Aprilia Tuono was very nearly my favorite bike ever, but it hardly ever ran. Instrument consol flooded every time it rained and shorted the bike out, battery died if not ridden every two days...list went on and on, so eventually gave it back to the dealer. When it worked though it was awesome, and I could have spent a bit of money on it and sorted the electrics, the ridiculously tall gearing etc but I got the shits with it letting me down all the time.