I wouldnt call season 3's episodes disappointing :
Too Many Pinkie Pies was a wonderful episode.
Scootaloo finally has Rainbow Dash as her big sister, but we can tell that Rainbow Dash may not be a good sister. Plus Luna has a power to go into ponies' dreams.
Rainbow Dash had a wonder character development episode.
Apple Jack finally has a solo song.
Trixie got redeem and finally had way better episode than the first episode she appeared in.
Most of all Twilight has finally grown as a character and the ending season 3 opens up the possibility of so many things!!