In Google webmaster tools you can: - see more backlinks as with link:domain - set your domain in the way, that all backlinks will come only on www. domain or only on domain. - create sitemap of your site, which makes it easier to crawl for google spiders.
main tool which i used is sitemap tool, which help to index your pages and get more information about back links, error pages and lots of other stuff.
I am frequent user of this tool and heavily really on this for my client's website analysis however, I sometime doubt if it presents true picture like link:www.------- and :www.------- returns different results for me.
First of all google webmaster is very effective tool to know: your sites back links, error pages, broken links, statistics of your main keyword performance and its rankings in google. Linke google webmaster tool there are tool available for yahoo and msn also...
I rarely ever use it, alot of the data is very slow to update so server side solutions are alot more useful.
It has lots of important tools for webmasters... You can access it if you have an account and try it yourself....
Google Webmaster tool is Gogle tool, it is not ment to be installed on a site. If you're using Firefox, you might want to instal 'SEO for Firefox', which tells you PR, backlinks, age of domain, Alexa traffic, and links to some keyword tools.
They provide vry important info abt yr site like: u can submit yr sitemap XML & update & knowing that any link is not broken, if u redirect any URL from yr site so u can remove that old url from google memory by URL removal Tool well knowing yr site internal & external links how u get another is yr KW search query that how many ppl use yr KW for searching & click on that other many... all secret i dont tell jst check it out wid enough time. Cheers