Newbie question re: USB quality

Thanks to everyone who has guided me to this point that I'm able to even ask this question! I'm learning quickly about computer audio and right now using a USB thumb drive with DSD files plugged into an OPPO 105 (non-Darbee edition). I'm getting good quality sound that is certainly superior to rebook CDs.

However, I've seen it mentioned in various articles on audio websites that USB as the interface has various weaknesses. Usually, this is just stated without any mention of other options. What other ways would I be able to get audio files to my Oppo. I have a Macbook Air, but other than connection via USB from the computer, I don't know if any other way to get files to the Oppo.

Again, I appreciate your willingness to help a technophobic newbie.

Best,
Scott