I have a somewhat spread out library and find that about 5% of what I have is not available. Most of the unavailable CDs are compilations or other strange CDs that are not very common. I try to submit as much as I can, for sure. I REALLY wish that it was a little better quality, too. I find that often times there are mistakes--about 1 in 10 CDs has a mistake, sometimes with terrible effects, and I always read through every song and quickly verify. I also wish people would make sure to input the correct year and follow a set pattern. For example, I think that all Volumes, Discs, etc., should be in (). I also think everything should be initial capitalized for simplicity. I remove extra information on classical music because it is annoying, as well. I'm pretty much done now, so it doesn't matter, but just something to mention. I am at around CD 490 with about 20 more to go, and I'm DONE! I've ripped and scanned every CD as best as I know how.
As I like to describe to my friends who think I'm crazy for using FLAC (I'm 18), this library will basically follow me for the rest of my life and storage will only get cheaper, so might as well do it right. Using flac also forced me to spend close to $1000 on CDs (all used!!!) to replace crappy itunes or low quality mp3's.