I just mastered a song in Bandlab's free mastering service, and to my ears, I think it did a reasonable job.
I had tried mastering the song myself but was not impressed with my own efforts. I then tried LANDR which only gave me a low resolution MP3 which was I thought was still better than my own effort. However, it requires subscription for higher quality masters for which I'm not ready yet.
I then found that Bandlab offers free unlimited masters in CD quality, and I'm already signed up anyway via Cakewalk. I then made a CD quality and a MP3 master and imported them together with LANDR's version, into Cakewalk to compare the differences. The LANDR version was just a dB or so louder, and perhaps just slightly darker than Bandlabs, but apart from that I couldn't determine much difference between the three versions.
So, has anybody else here tried these online mastering services and what are your thoughts?