We have used the Google Search Appliance to index and serve search results for multiple related properties. We allow it to crawl a marketing site and a repository of online product support content. Content from both sources may or may not appear in different search results, depending on the use case. Sometimes it's appropriate to serve results from a wider array of content, sometimes it isn't. In this respect, it has been helpful to segment/filter the results that surface as appropriate, using a single tool.
Pros
The GSA is able to organize collections of content in many different permutations, based on your needs.
The logs of searches and served results can offer insights into what visitors/customers are seeking, and whether they're finding what they need.
Default front-ends are relatively easy to set up - if they meet your needs.
Cons
It's my understanding that Google is ending support for the appliance soon. This is obviously an important consideration.
The administrator interface is far from easy to use.
There is a significant learning curve for new users.
Likelihood to Recommend
The Google Search Appliance is well suited to most site search needs and it is possible to customize the front end seen by website visitors to produce a satisfactory basic interface with basic branding applied to it. However, in some situations it may be necessary to instead make API calls from a web page to retrieve search results and the format in which those results are returned might be a little more difficult to work with.
