After a week or so of frantic rumour-mongering about an acquisition, Twitter has finally bought Summize, the search tool that everyone has been making use of for months now as a replacement for Twitter’s often-missing “replies” function. Now they can just go to search.twitter.com, which presumably will continue to work even if Twitter itself is down, just as Summize did — unless Ev and Biz move the search service onto whatever craptacular server setup Twitter is running on, which I find it hard to believe they will. The acquisition also means that Twitter now gets a bunch more engineers, who one hopes might be able to get the good ship Twitter back on course once and for all.

According to TechCrunch, the two companies have been talking ever since they worked together during the Steve Jobs keynote at Apple’s developer conference last month, and one of the investors in Summize was also an investor in Ev Williams’ previous company — a little blogging software startup called Blogger, which was eventually acquired by Google. According to Mike Arrington, the head of technology at Summize will become the CTO at Twitter, and hopefully bring some stability to both that position (which has seen a fair bit of turmoil over the past six months) and to the problem-plagued service as a whole.

As my friend Om Malik pointed out when the rumours first emerged last week, acquiring Summize and some of its search-related services could go a fair distance towards helping Twitter come up with an actual business model (it should, since Silicon Alley Insider says the company cost about $15-million). And if you want to find out what Twitterers think of the deal, all you have to do is check Summize. Summize founder and CEO Jay Virdy (the only one who isn’t joining Twitter) has posted some of his thoughts about the deal and about how Summize came to be.