My wife has now got her iPhone and the time has come to "divorce" our Apple IDs.  Previously, we have used my Apple ID for purchases, and have had Home Sharing on in iTunes so we can share our purchases (songs and apps) between our computers, my iPhone, her iPad and our iPod touch.  But with iCloud, it now seems to warrant us having separate Apple IDs.  I'm hoping someone can help sort out the muddle.

If my wife creates a new Apple ID for her iPhone so she can use iCloud (without interfering with my iCloud), she presumably needs to use this with iTunes on her laptop.  Will this mean she can no longer access the songs and apps she's purchased when using my Apple ID?

I've read that you can use a common Apple ID for purchases, and use separate IDs for iCloud.  Are there any pitfalls for this?