There's some official coverage on Google's Custom Search Blog [googlecustomsearch.blogspot.com]

Also, there's a feature list on Google's Site Search sign-up page [google.com]. Here's my short version:

1. Enhanced Index Coverage - crawl and index more content, even for pages deep within a site

2. Synonyms - upload synonym dictionaries specific to your website

3. Date Biasing - decide the level of influence that document age should have

4. Top Results Biasing - target the top search results from specific sections of your website

In the Reuters article, these two sentence jumped out at me...

Other features allow site administrators to add their own customized synonym dictionary, allowing Web site visitors to use site-specific terminology geared to a particular industry or culture....

...While the service encourages sites to customize site search results, the service does not affect the ranking of searches done via Google.com, which promises to keep search results impartial.

I'm not sure what the privacy terms of this offering will be. I'd guess that Google will be mining the search data and the customization data, most probably to help build its own lexicon and to help correlate web search with user experience on the site... ultimately with the intention of improving overall organic search results.

This basically seems to be an offspring or refinement of Google Co-Op. Here's the SiteSearch home page link that I find...

[google.com...]

When I looked down at the privacy policy link, it appears to be the old Google Co-Op custom search engine privacy policy.

[edited by: Robert_Charlton at 8:57 pm (utc) on June 4, 2008]

It seems like it is getting closer and closer to what the Search Appliances offer.

We've had it on our site since Mid May and we're very pleased. The detail to which you can search and get back viable results is astounding. As long as it's on the page, it'll be in the index and searchable in no time at all. To us, it's what we've been looking for in site search.

We do have to do some work on tweaking it just a bit, but no fault to Google as it's more of furthere utilizing the tools which Google provides to enhance the site search. :)

Also if you site has no search capability at the moment, you can enter a Prize Draw to win Google Site Search for free - [google.com...]

I've been using this for a couple of months and I have to say I'm very pleased with the results.

I'm very interested in the new custom synonym dictionary, but can't work out how to implement it - does anyone have a link to the documentation?

One problem that I've experienced is that the volume of searches on my site has gone down since I implemented Google Custom Search (previously I'd used Zoom Search). I have a feeling that this could be due to the Google logo in the search box - maybe some visitors just think it is a search box for the standard Google search engine. Although I've paid for the business edition and am allowed to remove the Google logo there is no easy way to do so. Really I'd like to replace the Google logo with the words "search this site."

We're in the process of implementing this on one of our e-commerce websites. Currently, when customers search on our site all they find are products. Now they'll be able to find products, news, upcoming events, blog posts, etc - it should be a good deal. I'll let everyone know the results.

Using site search gives Google even more information about your site and more space for penalties, so think twice before using a service like this.

So, does this mean that inclusion in Google will be faster and more complete if we pay for this service? It seems Google will not necessarily deep crawl, but if you pay for a service like this, it seems Google would almost have to do it for a proper Site Search.

...While the service encourages sites to customize site search results, the service does not affect the ranking of searches done via Google.com, which promises to keep search results impartial.

I'd say the answer is no - there's a "Chinese Wall" at work here between Business Site Search and regular ranking. Google can and will still choose not to keep urls in their regular indexes, even though they are available for this kind of custom Site Search.