I can really speak to any specific recordings, but I do know that in the New Age, Southern Gospel Genre that there are a lot of artist totally missing from the service.
I have posted artist list just using the latest Top 40 Southern Gospel chart toppers and out of that group there is like 7 artist on Slacker, the rest do not exist.
When you post in the forums the PD's don't respond. I've heard the support guys make excuses for them saying they have other jobs. But how hard can it be to get online for 30 minutes a week and respond to questions. I have to call BS on that.
In regards to most other Genre's I've been very happy, but have noted an artist or two missing here and there. I have also found that if I am hearing repeats, that I need to move my settings to auto because when I have it on hits or familiar then I am cutting the library almost in half. I am still very happy with Slacker for music. It isn't perfect by any stretch, but I am sure enjoying it. This morning I've been listening to a Vintage Country Station I made. WOW, I've heard artist and songs I've not heard since I was a little kid. Boy Patsy Cline, she had a voice sent from heaven! Amazing the music by her I've never heard play today on my station.