I had the same problem: Photostream enabled in iOS devices and MacBookPro SysPrefs but not showing in iPhoto (mac). I resolved this issue by following the directions above (disable/enable) after I reconfigured the settings on my iOS devices.
My Apple ID and my icloud account are linked, but not the same. Under iOS settings-iCloud I signed out/deleted my Apple ID, and signed in using my Mobile Me/iCloud account (.mac or .me account). As soon as I did this Photostream appeared in iPhoto 9.4.2.
This is how I signed in to iCloud on my devices:
MacBookPro: @me.com (iCloud converted from a MobileMe account, originally a .Mac
iPhone: @mac.com
iPad: @mac.com (iPad Calendars shows me logged in as @me.com)
Apple will not allow me to use a Me.com or Mac.com address as an Apple ID except on the iOS devices. I was able to purchase music on iTunes (iPhone) after signing in with @mac. It required authentication using my Apple ID (3rd party address).
Also, a persistent issue with Calendars resolved itself when I did this.