There have been apps that allow that for awhile though.
It has a browser on one side, and a notepad on the other.
Worked ok.
Anyway, I'm kind of of the opinion that split screen will mostly be a novelty on the iPad..
I think it's perfectly fine as is..
And I'm glad that you're happy with it. You don't have to use new features that don't interest or work for you. There are plenty of things Apple has introduced I think are a novelty or even useless--I'm looking at you, Siri--features that I disable the minute I get a new device. (My husband uses Siri all the freaking time. I don't get it, but hey, more power to him if he thinks it makes his life easier.) That's the beauty of having choices.
Me, I prefer being able to use the apps that work best for me for each purpose, and not having to use a third one-size-never-fits-all purpose-built app that inevitably has one killer feature and absolutely nothing else I need. That's a kludgy workaround if for no other reason than I would then need to transfer those notes into my normal working app, adding additional steps to my workflow.
I also don't just do work with websites. Reference books in ebook form are a big part of research for me--so a notes + browser only setup would be worthless in that scenario. As most of my ebooks are in Kindle and PDFs are in GoodReader, being able to pair those with Notebooks (or eventually Scrivener for iOS) on the same screen is going to smooth my workflow considerably.
Once third party apps support split screen, this will be a very useful feature for some of us who use the iPad more for production than consumption--for us, that one thing may well be worth moving up to a newer iPad. For those who only use their device for surfing, watching video, etc., I suspect it'll be a take-it-or-leave-it function they don't often use...certainly not a feature worth upgrading for.
Unless, of course, they just want someone to enable them. In which case, of course you should upgrade to the latest & greatest!