Label or no labels, I'll purchase from Google if they do the following:
1. Allow lossless music purchases
2. Allow purchased music to not count against your storage quota
3. Allow redownloading your purchased music "forever"
4. Price music well (by "well", I mean less than or equal to Amazon/iTunes/CDs)
#2-4 are probably a given, but I'm really not counting on #1 happening. Amazon doesn't do it and iTunes only has the ALAC* format. Google Music converts FLAC to 320kbps MP3 before uploading currently, so I'm taking that as a bad sign from Google for FLAC support. I'm just getting really tired of buying CDs and ripping them myself, so much so that my music purchases have gone down the last couple years**.
*ALAC is fine now that it's open source, but my Nexus S doesn't support that format natively. It doesn't support FLAC either, but Android 3.1+ added FLAC support, so I don't mind waiting for Android 4.0, which is coming "soon". Plus it was opened pretty recently, so I'm still waiting to see if how much software/hardware support it gets down the road.
**Remember that NFC chip on a CD case demo Google showed way back when (I think it was NFC)? i.e. tap the NFC to a reader device and Google will recognize the CD as a purchase and it shows up in your online account for playing/downloading. I wouldn't even mind that if Google went lossless, is that even available yet?