I have a similar situation as described in the original post but, after reading the posts in this thread, I still have some questions. I recently purchased iTunes Match and would like to share my iTunes Match with my wife. I've already ripped a lot of CDs and my desire for us to share libraries is as much about the simplicity and ease of having one library as it is cost. To rip the CDs twice or even copy all of audio the files from my computer to hers seems cumbersome. From the previous posts in this thread, it sounds like we could share the same iTunes Store account to accomplish this.
Questions about the impact of sharing an iTunes Store account:
How does one the change the Apple ID to be used with the the iTunes Store for a particular iPhone?
How does that impact apps already purchased with the previously used Apple ID?
Lastly, there is at least one app that we both purchased separately - a password manager app. Would using one iTunes Store account allow us to each still store separate data in our password manager app or would the same data for the app be synchronized to both devices then?
I would appreciate any help that can be offered!