I'll second what jedaisoul said -- There are bits of HTML 5 you will have shoved down your throat by Apple fanboys and freetards if you want media content -- like AUDIO and VIDEO; there are some bits that are useful it you're writing HTML 5 crApplets like MANIFEST, but beyond that, there's little if anything of value; the majority of it is the re-introduction of old redundancies (EMBED), introduction of new redundancies if you have the slightest inkling how to use numbered headings and horizontal rules properly (SECTION, ARTICLE, HEADER, FOOTER, NAV), or return us to 1990's style presentational markup practices (ASIDE).
... and that's why a lot of developers are now saying "design in STRICT first, then deploy as 5 if you must".
I prefer XHTML 1.0 Strict for it's more consistent and legible structural rules, but 4.01 Strict is equally acceptable. I've always kind-of hated the idea of the "empty" tags like IMG and META having no visible closing mechanism. Probably why I'm not wild about Python since even though I'm a stickler for tabbing of code, whitespace shouldn't be used as a structure mechanism.
Probably the old-school assembly language programmer in me, I like to see that RET, call to INT 21h AH=00, etc, etc... Closures man, closures.