An old answer to an old question, but one which has just helped me out tremendously. A true credit to the Q&A system!

I was under the impression that Open Graph data is completely separate from structured data, at least in the way Google is talking about.

There are quite a few examples of websites using both without any issue, for example:

http://www.telegraph.co.uk/culture/film/filmreviews/9257722/Dark-Shadows-review.html

This review features extensive Open Graph data, in addition to plenty of additional markup data, and this does not affect the rich snippets data which can be found by searching under the keywords "dark shadows review".

I too would like to know this, because I've been doing it for months now. I haven't noticed any rankings issues, mind you, so perhaps it isn't really a big deal?

Providing the data is the same, I can't see it hurting. I will be following this topic with much interest.

Nobody has any input on this?

So as of late I have been on something of a mission to mark up my news website with as much accurate and detailed Schema and Open Graph data as possible, in order to not only allow the search engines to understand my content properly, but also to ensure everything appears in the most ideal fashion when linked to from Facebook, Google+, etc.

Here is an example of a typical article page: http://www.nerdscoop.net/technology/video-games-459

As you'll see I currently have news posts marked up as article because that is essentially exactly what they are, but is there a better way to emphasise that they are news rather than just generic articles?

My second question is regarding the category pages and the home page. How would be best to mark these up? With OG the task is fairly simple, because I can specify the homepage as being a website, but not so with Schema from what I can see.

Either way, this is an interesting subject to me and I look forward to any discussion as a result. Thanks for looking.

I would agree with Marcus' answer on this one.

Another question as an off-shoot from this one would be: What is the performance loss in checking each request against your htaccess rules?

If the answer is none, or very little, then perhaps keeping the 301 forever isn't a bad idea at all. You never know how long people will be linking towards those 301'd pages. I personally have some pages just like this which have been redirecting visitors for as many as 5 years, because it's better to keep the link juice than to end up as 404s.