Description meta tags are important because Google might use them as snippets for your pages. Note that we say "might" because Google may choose to use a relevant section of your page's visible text if it does a good job of matching up with a user's query. Adding description meta tags to each of your pages is always a good practice in case Google cannot find a good selection of text to use in the snippet. The Webmaster Central Blog has informative posts on improving snippets with better description meta tags18 and better snippets for your users19. We also have a handy Help Center article on how to create good titles and snippets20.
On another note, we recently went through this same process with an entire site redesign. The executive team demanded we cut out over 75% of the pages on our site because they were useless to the visitor. It's been 60 days since the launch of the new site and I've been able to still increase rankings, long-tail keywords, and even organic traffic. It took a little bit of a "cowboy" mentality to get some simple things done (like using 301's instead of blocking the old content with robots.txt!). I predicted we would lose a lot of our long tail keywords...but we haven't....yet!
You should build a website to benefit your users, and any optimization should be geared toward making the user experience better. One of those users is a search engine, which helps other users discover your content. Search Engine Optimization is about helping search engines understand and present content. Your site may be smaller or larger than our example site and offer vastly different content, but the optimization topics we discuss below should apply to sites of all sizes and types. We hope our guide gives you some fresh ideas on how to improve your website, and we'd love to hear your questions, feedback, and success stories in the Google Webmaster Help Forum1.