Well, the code is neater...you can forgo a lot of the tags, you can read it easier - the semantics have been improved, so you know what you're seeing at a glance, it is more consistent spanning websites as it is now standardized....
well there are few amendments done in the previous versions of html which u can say as "advantages " which are nothing but the extra plug-ins which were needed to be downloaded from any external source previously ,are already included in html5...so it makes the coding quite easier..:)
I find this argument to be moot. Plugins allow the extra cruft to be viewed the same across all browsers since the plugin is the engine, whereas if its directly in the HTML as in HTML 5 it will be at the will of the browser, so expect designers to still have to find browser hacks especially with IE. But it should make coding easier, good point.
I am an XML fan and I believe with any markup language all tags should be closed since closed tags make your code less likely to be misinterpreted by the browser. Great point about the semantics though this will probably be the biggest factor since that is the most forward looking aspect of the web I think. Great answer.