E-consultancy.com site migration - SEO tips?

Sometime around the end of November, or early December, E-consultancy.com (this site) is due to relaunch.

It'll be broadly similar in content and structure to the current site but have a load of new stuff, a new design, a new brand identity etc.

The site will be hosted in the United States (currently in the UK) and will be at "econsultancy.com" rather than the current www.e-consultancy.com i.e. no 'www' sub-domain and dropping the '-'.

Effectively, then, in Google's eyes we could appear a new site, with a new domain, on a new IP range (in a different country).

Which, given our good natural search rankings at the moment, could well be tantamount to SEO suicide. 

We're keen to track, and publish, the results of what we do so that others can learn - possibly from our mistakes! I'm sure it'll be much more interesting if it goes wrong than if it goes right. Maybe if it all goes horribly wrong then at least we'll get a load of links to the 'new site' from the resulting PR ;)

The one thing we're concentrating on doing as well as possible is making sure that the correct redirects are in place, at a page level, so that PageRank should transfer from old to new. But we still might lose our overall domain credibility / authority. And, if so, we're not sure for how long.

What experience have others had of this? Any things which have turned out to be particularly important (or unimportant)? What's worked and what hasn't?

Regards

Ashley Friedlein
CEO
E-consultancy.com