LANDR is not _bad_ but there's one thing Landr site does not give any information: it can deliver masters to various online music sites but does it match adjust loudness levels optimal for the various places? Loudness war is over in iTunes, Spotify and Youtube and it's no use to bring levels up to the maximum anymore.
Quote from Landr site:
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Loudness
The last process in the mastering chain is usually a special type of compressor called a limiter. Limiters set appropriate overall loudness and creates a peak ceiling.
Limiting makes the track competitively loud without allowing any clipping that can lead to distortion.
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As far as I know, competitive loudness is not required in most places, exluding Bandcamp. Personally I prefer -14 LUFS level; it's loud enough for any phone, tablet, pc or hifi system but it still has enough headroom for peaks. Last time I used Landr it was not possible to set desired loudness level by numbers, only verbally. I don't know if they have improved the interface since then.
$299/year (Pro account) - not cheap but maybe it's worth $$$ for someone if you want not only master but also release music in iTunes, Spotify, Google Play etc.