i had the same experience with my shure e2c's, i went to these from sony's behind the head style headphones. and personally, i felt i was ripped off for being $99. After 2 weeks, boy did my opinions change.... maybe it was burning in, the way i started inserting them to create a better seal, or just the switching of diff tips. The bass was there and started to show well, and sounded great. Even now, after countless hundreds of hours, I am sometimes still impressed by the experience i get from them... but now going for something more, like a e5c.
I havent tried the ultra soft tips, but i have used every tip given in the package for about a week each to test them out. I decided ultimately with the foam, because of the way it feels after a while in that i barely notice its there and the ease with putting it on. As for isolation, i think all tips work well if you know how to place it in right, for foams provided a much easier use. Also, i found the foams to provide better bass with whichever position they were in my ear, for the others, they were picky in how they were for me to hear the bass well.