Amarok is stable on my setup, i.e., Kubuntu 11.10 with the kubuntu-ppa enabled (note I enabled the ppa for more stable Akonadi and Nepomuk, not for Amarok). The dependence on Mysql is an educated choice. The Sqlite in 1.4 was useless for medium to large music collections, and changing to Mysql was a hassle. KDE4 has chosen Mysql as the standard db for the desktop, so it is a shared resource, hence changing Amarok to use, e.g,. Postgresql would introduce bloat with no tangible benefit. One may question the choice of Mysql of course, but that is another discussion.
The stability issues that have bothered me significantly in Amarok are due to Pulseaudio integration. Finally, that also seems quite stable (cross fingers).