I've once again updated to the latest WordPress and still the conditionals in my sidebar do not return the expected results. is_tag does not return true in the sidebar for tag archives for instance. I've had this problem for many versions. It seems to occasionally get better or at least different, but it hasn't worked completely as expected for many versions of WordPress. I've just lived with it.
I put in all the conditionals up to a point and had them out put when they were true at the bottom of my sidebar. is_tag does not return true and my tag cloud does not get displayed for tag archives.
This is a blog started in 2005 so it has been updated many, many times, most recently to the 3.2.1 code base. Besides plugins that don't get along or function as advertise my blog is working as expected though I put a lot less work into customizing it than I used to. I've also taken to blogging at WordPress.com about specific topics as my blog is big and bloated and unfocused. I'd like to get the sidebar functioning as expected you can see the wacky behavior here: