Well, In addition to my other 2 posts reviewing these.
With 24 hours of burning-in the sibilance is gone. I still think these are very nice earphones, although they are still a little bass heavy, with a slight sucked in midrange. But, if someone had handed these to me and said they were a $100 earphone I wouldn't have argued much.
They don't have the detail of an ER6i, but I can't say it is worth spending 2-3x the cost of the FX66 to get the Ety's if you are on a budget. The ER6i on a cmoy bass boost or Penguin Caffeine with bass boost is more acceptable, but still can't quite match the bass on the AirCushion with the EQ off!
The FX33 are totally veiled and muddy compared to these, and mine have the same number of hours on them (24hr). These are brighter without being sharp, and punchier without being as muddy, and isolate better while being more comfortable.
I would have to say they sound totally unrelated to the FX33 - If you have JVC Marshmallows, Sennheiser CX300, Shure E2c, Bose IE, ipod buds, Koss plugs or Sony EX51LP (all the ones I have heard or have) - simply direct them to the trash can, and friend or the FS forum, and buy some Air Cushions...
If you already have some ER6i, just buy Shure black olive foams and a PenguinAmp.com "Caffeine" amp with bass boost.