Vitor, do you have the recently reshelled version of the SM3 or the earlier one? No dust in mine at all.
As for cheapness and fragility, yeah I get where you're coming from. They're very lightweight and demand a lot of gentle respect when handling, thats for sure. I figure they're probably more resiliant than they look, but I'm taking no chances. Time will tell - they're still pretty new on the market, after all, but Earsonic have been around for years and are very well regarded, so I put my faith in them.
Tipwise, I too sometimes find it tricky to get a perfect seal in my right ear with the stock double flanges, so I ordered and received a couple of packs of Jays single silicones this morning - medium and small. Have only had chance to try the mediums so far but they fit brilliantly and the sound, if anything, seems even better than the Earsonic silicones. More soundstage and air, without losing any frequencies.
Needs more time for testing though, so take that with a pinch of, um, dust.