I still remember getting my HTC Desire Z, rooting it and installing a cleaner custom ROM, then instantly looking for a decent music player on the Play Store that could handle music synchronization from iTunes. After days of research, I settled on PlayerPro and iSyncr, which would let me sync specific playlists from my iMac to my phone along with all the ID3 tags and metadata, even the lyrics and album art. And it took care of syncing back play counts to iTunes, which were used to improve the smart playlists it generated. I was practically using my Desire Z as if it was an iPod and it was revolutionary!
PlayerPro hasn't aged gracefully, but it's still quite a capable music player and it gets updated regularly with new features and functionality. To counter the skeumorphic interface with old iconography and layouts, there are skins by BlastOn SA, ikorolkov, and Player Skins that can improve the interface, if only a little bit. If that works for you and you're not into the MaterialAllTheThings! mentality, you might be happy to know that the paid version of PlayerPro is now on sale in the Play Store.
It usually retails for $4.95, but it's down to EUR 0.10 in France, Germany, Italy, and Spain, GBP 0.10 in the UK, RUB 10 in Russia, and AUD 0.20 in Australia. Like many of the recent deals we've posted, it's not discounted in the US or Canada. It might be down in some other countries though, but these are the ones we've verified.