After working with this a bit, I think that it is excellent. It replaces the real clunky search process that Rootsweb still has linked on their main page - where you have to search by list, and then by year.
With this new search engine in the Keyword tab, you can search on keywords - and get results from all mailing lists. The "Search tips" read:
* Search for a phrase by putting quotes around a group of words, like "john jones"
* Perform a single character wildcard search using "?". For example, j?nes will find jones and janes
* Perform a multiple wildcard search using "*". This will look for zero or more characters, so jon* will find jon, jones, and jonson
* Use "AND" to require the search to find all words or phrases.
"john AND jones" will only return results with both words
* Use "NOT" to exclude words or phrases. For example "john NOT jones" will return all results with the word john but not jones
If you use the Advanced Search tab, then you can narrow the search to words in the title, words in the body, an email address of the submitter, a specific mailing list, or a date range. That is a MAJOR improvement over the previous search capability.
I counsel patience as Rootsweb/Ancestry improve their products - and if you want to make constructive suggestions to their Help Desk at http://helpdesk.rootsweb.com/ I think that they will listen!