I have a website that generates its title tag dynamically. the title tag is in unicode format. the title tag is limited to 65 character but sometimes Google doesn't show title tag completely in SERP. I'd like to know what is the optimum length of title tag in terms of seo for unicode titles, and is there any difference between Unicode title and non-Unicode title tag? And what about other search engines Bing, Yahoo and so on.
google will truncate title tags if they are over a certain length so the old rule of 70 characters max is not 100% correct any more.
By length i mean px length so if your title had a lot of words with A K L ect ect rather than l or i then it would take up more space.
there have also been instances that if your title tag is too long google will disregard it and take its own from the content or url
for more info see this blog post on seomoz http://www.seomoz.org/blog/long-title-tags