The RP-HTX7s are notable for their clarity and generally well-balanced sound. If you're into big bass, these probably aren't the headphones for you, but they do deliver an ample amount of low-end and it's pretty tight, especially considering the price of these headphones. While the headphones are fairly even-keeled, there's a little bit of treble accentuation (they're a tad bright), which can lead to a slightly harsh edge when you dealing with tracks that aren't particularly well recorded. Or, to put it another way, the headphones will make bad-sounding tracks sound worse. By the same token, well-recorded, lossless tracks will bring out the best in these headphones.
We review a lot of headphones here at CNET and are always on the lookout for models that deliver a lot of bang for the buck. The RP-HTX7s fall into that category -- especially if you can get them for $30, their current low price online (note: you have to add them to your cart at Amazon to get that price). Needless to say, you can't expect the world from $30 headphones, but if you're on a tight budget and still want something that sounds good, this set will certainly fit the bill.
Are they better than the slightly more expensive Audio-Technica ATH-M30s? In some ways yes, in other ways no. The Audio-Technicas have a warmer, more laid-back sound, with bigger bass (I give the nod for sound quality to the ATH-M30s). They're also slightly more comfortable to wear over extended listening sessions. But the Panasonic sets' sound is a bit more detailed and aggressive, which is how some people like their headphones. The RP-HTX7s are also more suited to mobile use, with a less bulky design and a significantly shorter cord that's thick but not too hefty.
Add it all up and you're looking at an excellent pair of entry-level over-the-ear headphones. No, their design and sound won't appeal to everyone, but most buyers should come away feeling like they got a great bargain.