I strongly encourage you to wait until most wallet software supports replace-by-fee before doing that, because until that happens replace-by-fee just makes it easier to steal from bitcoin-accepting merchants.

I will tell you the same thing about 8MB blocks: until most merchants support bigger blocks I will strongly encourage you keep creating less-than-1MB blocks. If we want Bitcoin to succeed more quickly, we should all be thinking about what is good for the whole system: users, merchants, exchanges and miners.

As always, if you have questions or concerns feel free to email me.