I'm trying EBC grooved discs, and haven't noticed any extra noise; however, they seem to be a lot more resistant to wear than the OEM lexus discs. The EBC redstuff pads I've paired with them are quiet, stop well and are a lot less dusty than OEM (but even these produce quite a lot of dust).
My understanding is that lexus use very aggresive pads (because the IS250 has undersized discs). Because these wear discs so quickly, it's not uncommon for OEMs to specify the lowest grade of disc available, on the basis that the wear from these pads is so severe, higher grade discs will still end up getting demolished; so if the discs are sacrificial, they might as well be the cheapest possible.
High-end aftermarket discs are usually made of a very hard grade of iron, so may be more expensive than the OEM discs - whether they are good value is open for debate. My hope is that the ceramic restuff pads are less aggressive than the metal-filled OEM pads, so that I get a lot more use out of these expensive discs. This is yet to be proven, but my initial impression on 4000 miles of urban and country road driving, is that they certainly aren't worse, and are probably a lot better.