Whether it's right for you is really dependent on your situation. You know what the features or iCloud are, so the question is really one of whether your wife needs to have those features for herself rather than shared with you.
As to your other questions and comments...
I'm not absolutely certain about iTunes Match. According to the FAQ, iTunes match is tied to the Apple ID used for the iTunes purchasing account and supports up to 10 devices. But it isn't absolutely clear to me by their description whether you must be signed into that Apple ID for iCloud, iTunes or both.
This article talks about using different Apple IDs for different services.
This one shows how to add an iOS device to iTunes Match. If I follow these instructions, it asks me to sign into the iTunes store, whcih makes me believe that is the primary identifier.
In any case, you could always change it back if you wanted to.