You basically have to have all of your seller accounts set up. I think we have 17 different markets although some are combined through Alibris (specifically for books). If it sells on one market it will delist on the others automatically.
Listings are automatic...i.e. scan the book, cd, etc. and it gets listed. You can set up several pricing rules like average of lowest 3, lowest by a penny, etc. They do take a cut though so if you aren't clearing 100-200 items sold per week its not worth your while. My wife and I never have enough books or cds at one time to stay continuous. She usually only lists the 4 or 5 out of 20-100 books you get in a locker because only 4 or 5 are worth anything. For us the minimum is over $3 and a rank of 350k or less. The rest I just take to work to recycle.
If your buying pattern nets you a lot of books or cds (we usually find empty cases with the exception of the last run) or you have a good source of books like picking, auctions, libraries, etc. it is definitely worth it. The repricing alone is worth it. You don't always have to manually reprice.
One word of caution...they do charge a percentage of sales. I don't know what that rate is ...ours has been negotiated because of the large volume (my day-to-day job...not from SUs...my wife's job). I am not endorsing Monsoon. I am suggesting that if you have a lot of cds and books it makes things a lot easier and you can increase margin pretty significantly. It is a good option. They have competition with
http://goindaba.com/ which used to be a mass of php scripts but it is probably much more mature software now. Haven't looked at it for 6 or 7 years though.
...that is what I know in a nutshell.