Priming our IDs and Systems for iTunes Match... Best Prac?

Question

Hi all,
I love the concept of iTunes Match and plan on subscribing, however I am aware there might be pitfalls due to our (not so unique) setup at our house and I am keen to ensure I set things up correctly to avoid headaches.
I'm hoping you all and your seven months of consuming this service will help me!!
Firstly, I'll describe our setup.
2 people. 3 Apple ID's (1 each + 1 shared iCloud).
2 Work PC's. Windoze.
1 iMac (home). Lion.
1 Macbook (home). Snow Leopard.
2 iPhones
1 iPad.
Currently my fiance and I use our individual Apple ID's to purchase songs and apps that suit our own tastes. We share an iCloud ID across our iOS devices and iMac (which allows us to sync calendars, contacts, photostream etc).
Currently our shared iCloud ID has 0 computers or devices authorised to play content purchased with its ID as no purchases have been made (outside of some apps on the iMac).
My personal Apple ID has 4 computers and 2 devices authorised. (iMac, Macbook, No Idea 1, No idea 2, iPhone and iPad).
My fiance's Apple ID has 5 computers and 1 devices authorised. (iMac, No Idea 1 through 4, iPhone)
What I am trying to determine is how we should prepare for and configure iTunes Match.  What we would like to do is use iTunes match on our personal devices (of course) - the iMac, Macbook1,1, 2 x iPhones and our iPad.   We'd also like to use iTunes match on our Work PC's so we can listen away to our own music while we slave away, noses to the proverbial grindstone, for WAY too many hours each week.  This would use up 4 computers and 3 devices from our ten licenses.
Firstly, should we both de-authorise all devices from our iTunes accounts?  As I understand it this would clean the slate for us in terms of authorised devices.
However, I'm aware there's some 90 day doohickey to slow down using multiple ID's on a computer.  So an option here would be to de-authorise (and then re-authorise the iMac) for my fiance's account devices... and wait 90 days to do the same for mine, considering I have one computer up my proverbial sleeve.
Secondly, which Apple ID should we use for iTunes Match? It seems to make logical sense to use the shared iCloud ID.  However, as no music has been purchased using this ID, I'm not sure if this will complicate things (despite the computer we would upload from using this ID as its iCloud ID and being authorised to play the songs purchased from both our accounts).  Can't seem to really find any documentation to clarify this.
Thirdly, and this might just be my idiotness, but I can't quite work out if a model of using our shared iCloud ID for match, but then continuing to purchase music from our individual Apple ID's will actually even work.
Finally - to put it most simply, I really don't know what I don't know here.. so if there are any things you believe I should be considering or any tips or advice or recommendations you believe would help me, I'd really, REALLY appreciate to hear them.

Answer 1

Okay - just been through the EXACT same thing.
AppleCare just advised me of the situation and here is my summary for you:
Despite supporting a different iCloud ID and Apple ID for store purchases on one device simultaneously, you will run into issues with this model.  I just have. i.e. While iCloud ID's can be different to Apple ID's and treated as such by some Apple services - iTunes doesn't work this way.
I used our shared iCloud ID to sign up to iTunes Match and while this worked, here are the pitfalls:
- On your Mac: You cannot be signed into iTunes Match with your iCloud ID and the iTunes Store with your normal ID simultaneously.
To continue to use your current model of ID management - you will need to make iTunes store purchases with your normal ID, then sign into iTunes Match with the appropriate ID to allow these purchases to upload to the cloud.
- On your iPhone: You cannot be signed into iTunes Match with a different ID to that which you are signed into the App Store with.
You would need to either use your iTunes Match ID on your phone to access your Music, or revert back to your normal ID and just use "playlists" etc to sync your tracks as per usual.
- You will be able to use the iTunes Match on your Work PC's.. so long as you don't try to sign in with your normal ID also. Or first. Remember that 90 day rule thing and sign in with the iTunes Match ID on your work PC.
The AppleCare staffer said we're not alone (obviously) and that he hopes that in time Apple will look to supporting account merging etc. However, they don't right now.