Meh...
I like my EX-70's. I only use them when I'm on the bus, or at work. When I'm at home, it's A900 using a PIMETA all the way.
If you like bass, they're good for that. However they are really bloated in the midrange IMO. As for sound isolation, they're great. Just enough, not too much, and not too little. The highs are a little harsh sometimes. I'm sure there are better and more cost effective options out there, but also, these look pretty cool.
My only regret was buying them from the Sony Store before I even learned about this place. I spent WAY too much money on them. These buds were my best friends during college while working away on my laptop. Programming (which I hate) is so much easier with good tunes.
Last note: If all you've ever used was stock earbuds that came with your walkman or something, they will be a nice step up from that. But then you'll start wondering what else you've been missing. Ignorance is bliss.
Bottom line: There are better buds out there. It all boils down to preference and your wallet.
[EDIT] Oh and next time try to use the search feature. It comes in handy and this topic has been discussed many times before.