I cannot report recent personal experience, but I have followed many discussions about such moves.

For most people, changing domains is the most dangerous action possible for a successful site, virtually never justified in SEO terms (or any other).

Even if the 301 is set up correctly:

from olddoman.com to www.new-domain.co.uk
from www.olddomain.com to www.new-domain.co.uk
from new-domain.co.uk to www.new-domain.co.uk

And you have avoided any major structure or content changes during the move,

There will ALWAYS be a temporary problem as Google assimilated the new site, and on occasion the new site gets the full "sandbox" treatment. For most sites, it'ssomewhere in between; sites with zero changes will tend to do better, it seems.

A new site is a new site; done right, you can minimize the problems - but I know of no guarantees.

I can speak from personal experience in transfering hundreds of domain names.

The new one is never as good as the old in terms of link popularity and ranking. It just isn't.

Now, it can be over time, but you have to gain it back. My best estimate is about 65% of your work transfers over, and you will realize about a 40% overall drop in SERPs traffic.

Cabo

Within a few months, most of your PageRank will transfer over, but it may take up to a year to reestablish your TrustRank. Re-branding is not something that the search engines consider, they just don't like it when URLs change -- and neither do searchers, previous customers, or people who've bookmarked or cited your pages.

Best of luck,
Jim

Thanks for the replies guys.

The thing is, Yahoo and MSN have followed the 301 fine! No loss of rankings there. Just Google.

Oh well, choices to make.

I agree with cabowabo, only I think the number is even lower - you perhaps get half of your rank after a few months.

I've heard estimates of ~10 months for the transfer of as much of rank as you will ever get transferred. I think they are pretty accurate. In my experience, it happened in 9 months, but as cabowabo pointed out, it wasn't a complete recovery.

Now, just to play devil's advocate: 301 is what Google tells us to do in this case. I've heard other suggestions, namely 302. Anybody tried that across domain names and if so, what were the results?

I remember in one of the recent Matt Cutts videos, he mentioned that age of a website plays a factor as "you can't fake age". Even though you are rebranding, Google may look at this as a "newer" site.

301 is what Google tells us to do in this case. I've heard other suggestions, namely 302. Anybody tried that across domain names and if so, what were the results?

I've had several sites brought to me that used a 302 redirect to point to their new domain -- what usually happened is that the old domain name stayed in the index and the new domain name rarely showed up at all, even after many months or even years.

Sometimes after URIs using the new domain name gained many backlinks, it would then be shown in the index. But then Google had a mish-mash of old domain and new domain versions of URIs for the exact same content, and all their duplicate content filtering kicked in.

A 302 redirect usually indexes the content of the new domain target page as belonging on a URI that uses the old domain.

I rebranded a few weeks ago. It was a .info to a .com domain name change and therefore completely necessary IMO due to the future aspirations of my site. I also secured quite a few variants to protect myself.
No structural changes were made and a simple htaccess was implemented to 301 every page to the new domain name in it's current structural format.
Google picked it up within 3 days. after 2 weeks, the old URL was completely gone from Google. The new homepage appeared straight away in exactly the same position for my test/benchmark keywords. However, subdirectoriues that were previously getting first page results are now nowhere to be seen. I expect this is a trustrank thing.
Overall, I have lost about 60 percent of my unique traffic but I'm not concerned because it was crappy traffic before anyways.

Regarding indexing, the new URL is much better indexed than the old in terms of accuracy and around 40 new pages are being cached each day. I hope I'm not tempting fate when I say this but I feel confident about this move. However, I think it rather unfair to take away the trustrank as the website has not changed and has been there for some time... what is the advantage to Google to deny that websites previous existance?