First of, read this.
Secondly, saying 24/192 is totally useless isn't completely true either. Some of the original mastering and remastered music from HiRes site are better mastered and only available in HiRes format, so getting the 'better' music does make sense. But it has less to do with bitdepth / bitrate and more to do with the mastering technique. With the right mastering, the difference between 16/44.1 and 24/192 isn't really that big, if at all. But 24/192 decoding still provide some other hardware based benefit that can be positive to SQ, however a bit of clever engineering can make sure the same benefit applies to 16/44.1 material as well. In the end, it really isn't about 16/44.1 vs. 24/192 but good mastering vs. bad mastering and good engineering vs. bad engineering.