hugh - 2:20 am on Feb 28, 2013 (gmt 0)
I completed the migration yesterday. Notable steps included:
1. 301 redirect of all URLs from from domain a to domain b in like for like.
2. Updated as many internal and external links as possible to the new address.
3. Create google analytics and webmaster tools accounts for the new domain including site maps and told google the web site had moved.
4. The old domain will remain indefinetely point to the new address.
5. Checking webmaster tools regularly for errors and so far no 404s.
6. Found a recent post form matt cutts or google stating categorically that the age of a domain was not a factor in the rankings but a change of ownership was (not the case here, this is a brand new domain).