It's not bad per-se, but there are several things I can nitpick against MDR-10R:
1. Overall performance. Very recessed Midrange, vocals and some of the upper-mids sounds very recessed in light of really boosted bass. In and of itself isn't a killer, but even at current price range of $100, you can find headphones of similar price that blows away the MDR-10R/RNC with more balanced approach. Yes, they are the usual suspects, but they are that for very good reason. NC function also falls behind similarly priced cans from Audio Technia (ATH-ANC7bs can be had as low as $130-$150)
2. It is very source specific in terms of things. It works quite well with portable Apple devices and certain frequencies that can be altered. For instance, it works quite nicely with Treble boost on Apple devices. Conversely, it doesn't work well with Samsung devices with similar EQ types. There doesn't seem to be any sort of consistency in the performance of the phones.
Don't get me wrong, I'm using them and enjoying them, but Sony's done helluva better for that price (MDR-ZX700s immediately comes to mind).