I agree with most posts here, if Calibre is doing what you need it to do in it's current form, don't upgrade.
I for one, am also an upgrade ho! LOL! Especially with all the new plug-ins that have elevated my Calibre experience onto a whole different level! The plug-ins have made managing my library so simple and I say THANK YOU again to everyone involved.
Bottom line, do what is best for you. If it ain't broke, don't fix it.