As far as earbud headphones go (not IEMs) I've found the iBuds to be just as good as anyother earbud. I've tried the MX400, MX500, MX550 and lots of Sony earbuds (not the E888s though). The thing is, earbuds just don't seem to sound very good (maybe my ear canal is shaped in a sub-optimal shape for earbuds...). Now before I'm flamed, IEMs, open fullsized, closed, etc... all blow the iBuds away. They also blow all ear buds away, earbuds are what this criticism is about.
I think people discriminate against iBuds since they are pack-ins and people ignorant about headphones tend to be fond of them. Personally, the only thing I have against iBuds is they are a bit too flashy (they just advertise you're listening to an iPod).
There has been alot of praise over the Sony E888s, but I have not heard them. They may be the holy grail of earbuds (I'd hope so with their price). But I did not find any of the Senn MX earbuds to be worth their price when I had a pair of iBuds that sounded just as good.