I heard the SE 420 at the San Jose show and thought they were outstanding. You might prefer them over the SE 530 if you find the 530 a bit bass heavy. Both of these Shures had a lot of treble detail, seemed linear and musical, with good bass detail. I'm pretty happy with my UM2's, but the UM2's are definitely a little bit euphonic by comparison, with a looser bass, on the iPod anyway, and less treble "air". I do feel that the UM2's are more forgiving on lesser quality recordings or low bit rate recordsing than the 420 or 530 are. That is, I was left unsure that a 420 or 530 would be appropriate for someone using an ipod at 128 bit rate. I felt that the 210 or 310, single driver units, were less demanding of the quality of the original source material.
Overall I liked the entire Shure SE line - which surprised me a bit, given that I'm very critical. But as I said, I think you need to match the unit to the quality of the source.
As for value of the Shure units - are they priced right - well they are not priced too low, IMHO, for their sound quality. I don't think the pricing is outrageously high for the quality, but I think that's very subjective.
Finally, I should also mention that I find the generation two of the nano and shuffle rather lean sounding, and so a slightly bass-heavy unit like the UM2 is a good fit. The gen one units of nano and shuffle, and all the hard drive based units seem to have a sonic signature that is less lean, to my ear anyway.
Art