This tutorial by Michael Bloch for "Taming the Beast" talks
specifically about how the 301 redirect page is the best choice for
preserving your search engine ranking:
"The 301 redirect is the safest way to preserve your rankings. On the
next spidering, the search engine robot will obey the rule indicated
in your .htaccess file. The search engine spider doesn't actually read
the .htaccess file, but recognizes the response from the server as
valid. In the next update, the old file name and path will be dropped
and replaced with the new one. Most importantly, the 301 redirect is
recognized by the mightiest of search engines - Google."
Tutorial - Giving search engine spiders direction with a 301 redirect
by Michael Bloch
According to this information, it sounds like you've done exactly the
right thing in creating your 301 redirect.
Google provides information on how changing a URL will affect ranking
in its search list:
"We cannot manually change your listed address at the exact time you
move to your new site. There are steps you can take to make sure that
your transition goes smoothly, however. Google listings are based in
part on our ability to find your site by following links from other
web pages. To preserve your ranking, you will want to inform any sites
that currently link to your pages of your change of address. As long
as the links change as you move your site over to a new location, your
PageRank should not be adversely affected.
If your site goes unlisted for a time, this does not mean you were
intentionally dropped from our index. Sometimes in these transitions,
we fail to find a site at its new address. Just be sure that others
are linking to you and we should pick you up on our next web crawl."
Google Information for Webmasters
According to this information, as long as you DO include a redirect to
your new URL, your ranking should be preserved. Google also provides
information on how it links to an "old" page:
"If we continue to list an 'old' version of your site (i.e. we
continue to list www.my123site.org despite the fact that your site now
lives at www.my456site.org ) you need to update the links that are
pointing to the sites. Since our robots jump from page to page via
hyperlinks, someone must still be linking to the defunct page. Once
others correct their links, we can too. Once your new site is live,
you may wish to place a permanent redirect (using a "301" code in HTTP
headers) on your old site to inform visitors and search engines that
your site has moved.
One way to determine who is linking to the dead site is to try a link
search. You can find instructions on how to do this on our features
page. Please note that this process does not work for all of the sites
in our index."
Google Information for Webmasters
You can use a special Google tag in a search to find out who is
linking to your site, or your old site:
"Who links to you?
Some words, when followed by a colon, have special meanings to Google.
One such word for Google is the link: operator. The query link:siteURL
shows you all the pages that point to that URL. For example,
link:www.google.com will show you all the pages that point to Google's
home page. You cannot combine a link: search with a regular keyword
Google Web Search Features
The method by which Google ranks each Web Site is here:
PageRank relies on the uniquely democratic nature of the web by using
its vast link structure as an indicator of an individual page's value.
In essence, Google interprets a link from page A to page B as a vote,
by page A, for page B. But, Google looks at more than the sheer volume
of votes, or links a page receives; it also analyzes the page that
casts the vote. Votes cast by pages that are themselves "important"
weigh more heavily and help to make other pages "important."
Important, high-quality sites receive a higher PageRank, which Google
remembers each time it conducts a search. Of course, important pages
mean nothing to you if they don't match your query. So, Google
combines PageRank with sophisticated text-matching techniques to find
pages that are both important and relevant to your search. Google goes
far beyond the number of times a term appears on a page and examines
all aspects of the page's content (and the content of the pages
linking to it) to determine if it's a good match for your query."
Google Technology, Page Rank Explained
I hope this has helped and please do let me know if you need any more
information before rating my answer.
Thanks again, it has been my pleasure researching this for you, and
good luck with your additional site!