Kind of a stupid question, but will messages from the same contact sort itself in the same thread regardless which address they use? I really don't want to have separate conversations clogging up the messages app...
Not a stupid question at all. In theory everything should be merged, but in practice - unless iOS 8.1 has fixed this - it didn't work that nicely. Messages on OS X properly merged conversations, but on iOS I always experienced split conversations. It wouldn't normally be an issue, because once a conversation is started then it will continue that way, unless someone intentionally starts a new conversation to your other contact information. Every now and then, however, my phone would message a reply to someone using my other information, instead of my phone number. It was a nuisance normally, but it became horrific in group conversations. It was for this reason that I (and I suspect, many others) disabled their email addresses for messaging and set all of their devices to only use their phone numbers.
SMS forwarding is a good enough feature that I'm willing to risk it. Let's hope that Apple has gotten it right this time.
