The problems with HTML5 are two-fold.
The first is that there are too many browsers out there in the world that don’t support it, or don’t support all features.
Uh, the core of HTML5 is just HTML4 with frames and some text formatting discontinued (in favor of CSS formatting). Otherwise, unless someone intentionally uses one of the new HTML5 tags, their “HTML5 file” will be perfectly understood by any standards-compliant browser now (and maybe even Internet Explorer but I would not hold my breath LoL).
Which is why I advised learning HTML4 with all text formatted by CSS. Everything one is learning in this way is in reality, by definition, HTML5. And any work-arounds would be done in external files that could be stripped away as they are no longer necessary without affecting large bodies of code.
When the more advanced features of HTML5 are reasonably well supported, folks can move on to learn them without having to get past that, “Gee, I have to learn a whole new language?” barrier. They’ll already have learned 90% of HTML5 (or HTML6 … you know committees!
).
I’m not talking about new releases, but what people have installed on their computers and are using. Sure, you’re always going to get a few oddballs who are still using IE5 in the 23rd century, and you have to draw the line somewhere, but the dangers of using HTML5 features are still high.
This is not the issue it once was, at least in the Windows world. The tight integration and rabid desire to possess the Internet have caused Microsoft to force users to upgrade their Internet Explorer as they move through OS versions. My understanding is that Windows 7 forces the user to IE 8 and the next OS release will force IE 9 on the user. I could be wrong here as I’m still glued firmly to good old XP SP3 and IE 7 (for testing only). Rock solid and runs like a champ. My basement computer has been running 24x7 now for 6 months without a restart. Try that with Win Vista or 7. LoL.
As regards standards-compliant browsers, they continually update themselves so support for new features is always being added or improved. Frankly, IMHO any developer who isn’t developing to Firefox 3.6 or 4 and “work-arounding” for the rest is just doing a whole lot more work than they need to. Sure, that could change but it hasn’t yet to my knowledge.
The second is that the specs aren’t finalised, and investing too much time and energy in developing a site to the current draft may leave you flat on your face when the specs change in a subsequent revision, and your site stops working on newer browsers.
Sounds like you’ve had quite a few problems with Internet Explorer over the years. No duh! You have to keep in mind that IE was not designed as a browser so much as a marketing tool to herd users into the Microsoft fold. Why do you think they integrated it so tightly into their OS product and force corporate organizations to use it (because only IE can properly log into a Microsoft corporate server domain as it requires some extremely non-compliant HTML coding).
And I suspect if one waits for finalized specs, one’s pages will be nearly obsolete before they are released. I was using HTML4 code years before it was finalized.
I doubt that standards-compliant browsers will ever actually discontinue support for frames and other common HTML4 tags if only because there are so many of these pages out there. That is one reason I stay away from exotic tags unless they degrade peacefully and the Customer really really really wanted them for some reason beyond my comprehension. LoL
You were doing so well until that point! W3Schools has a mediocre online reference. It’s easy to read and understand, sure, but it’s also got more than a handful of mistakes, it’s quite outdated and doesn’t always advocate best practice. Sitepoint Reference is a much better place to look for accurate information.
No question, both have their strengths and weaknesses. W3Schools is much easier to navigate, has a live practice panel for nearly all of the tags, and covers a lot more topics. And while the expanded commentary may offer further elucidation and the compatibility tables are nice, Sitepoint is not totally error-free either (check out the description for the ins tag). Both sites are just tools in the toolbox, not mutually exclusive information sources. And, if you do find an error in either, one might assume you would be good enough to report same, just as you would appreciate knowing about errors in your own pages.
IMHO, “best practice” is highly subjective and often changes with each “expert” that blossoms. I think being open to new ideas is fine but chasing after every single one is nonsense. Didn’t I just read a short time ago that the experts are replacing the über-popular “multi-column” CSS template with something new and improved? I say pick something you like and stick with it until you run across something you like better for reasons that actually make sense to you. K.I.S.S. is my guide. But then I don’t program any sites like Amazon.com so I can leave all that fancy brain-numbing coding to the freshly graduated CS majors. 
@TheRaptor: I agree. Why muck about with this DOCTYPE stuff anyhow? CoffeeCup HTML Editor just sticks that stuff up there automatically and I don’t pay any attention to it after that. 
And now I must really shut up and stop harassing you good folks. I’m sure we all have better things to do – my wife certainly thinks so
– than kick this topic around more. ciao