Yesterday, I opened my review of Windows 8 with an introduction to the new user interface — the main difference between Windows 8 and its predecessor. But while the UI is a pretty major change, Windows 8 signifies an even bigger change to the Windows 8 ecosystem.

So, when October 26th comes, should you upgrade to Windows 8? Read on to find out.

The new Windows ecosystem

We have entered the age of the ecosystem, with the most-complete options coming from Apple, Google, and now Microsoft. An ecosystem spans hardware, (phones, tablets, PCs, gaming consoles), software (email, calendar, apps, documents), and even entertainment (iTunes, Google Play, Xbox Live). Each of these ecosystems takes a slightly different approach, and most of us use pieces of all of them, plus a few things besides.

Apple’s idea of an ecosystem is to provide all of the hardware and then customize the software (or allow developers to customize) for each platform. The data syncs, but the software that manipulates it is tailored to the unique strengths of each device. It is by far the most complete ecosystem, because you can buy only Apple hardware, buy all your software from Apple (most of which could be made by Apple), and buy all your entertainment from Apple.

Google’s idea of an ecosystem is the cloud. Google doesn’t particularly care whether you use a Macbook or a Windows PC; it let’s you log into your Google apps from anywhere. However, it also has the biggest share of smartphones through its Android operating system, and it will soon start manufacturing its own phones and tablets through its acquisition of Motorola. You can’t stick completely with Google, but you can come close. (I’m leaving out Chrome OS devices, which are viable only for the most adventurous cloud users.)

With Windows 8, Microsoft is bringing its own ecosystem together, and it looks a little different. Like Google, Microsoft primarily makes software, not hardware. Through Windows and Office, it has a huge share of the PC market (yes, Macs are PCs, too, and plenty of them run Office). It even has a slice of the smartphone market with its Windows phones. Unlike either competitor, Microsoft is unifying its ecosystem on a single OS, so that you can do the same work on a phone or tablet that you can on a PC.

This makes for a bit of a disjointed experience, as I explained yesterday. Windows 8 feels like it has a bit of a split personality. Still, it promises a much more complete integration of your mobile and desktop computing. With an iPad, it’s still awkward to do basic things like edit Word documents. On a Windows 8 tablet, that will be basic.

Still, the success of Microsoft’s approach is going to depend on third-party developers. The trick to making mobile work is not giving people to their traditional software on a tablet. Microsoft has been trying that for years, but using Word with your fingers just plain sucks. It’s much better to have touch-optimized versions of traditional software. Look at Garage Band, Keynote, iPhoto, iMovie, and Photoshop Touch for iOS, for example. These are powerful apps that stand on their own, but that also have compelling desktop software counterparts. Unless developers put together compelling apps for Windows 8, it will fall flat.

And that’s where Windows 8 is weakest right now. If you want to get an idea of the strength of the Windows 8 ecosystem, just click on the Top Free tile in the Windows 8 store. How many of those app do you recognize? Did you find apps from the things you use every day, like Facebook or Twitter? Yeah, no. This could change significantly by October 26th — and it better.

Should you upgrade to Windows 8?

It’s easy to see why Microsoft felt like it need to create the Surface tablets. Without them, it’s hard to see the point of Windows 8. The apps, which are build with touch in mind, not a mouse cursor, feel out of place on a PC, where the desktop UI paradigm still makes the most sense. But they would feel right at home on the Surface, and the Desktop app — where you can still get to your traditional software — becomes something you use only when you have to get traditional things done.

Unfortunately, unless the Surface turns out to be mindblowingly better than I anticipate, it isn’t going to be the kind of thing you want to use for getting legal work done. I can’t imagine drafting a brief on a 10″ screen using a keyboard cover.

Windows 8, then, is as much a statement as it is an operating system: Microsoft thinks mobile devices like the Surface will be as much a part of our computing as PCs. Unfortunately, in Windows 8, the getting-real-work-done portion of the OS — the part you will use for drafting contracts, briefs, and bankruptcy petitions — feels like it has been shoved into a back room. (Which, ironically, leaves Apple’s OS X as a more friendly user experience for getting real work done.)

So, if Windows 8 puts most legal work into the second-class citizen portion of the OS, should you upgrade?

It depends. If you are using a version of Windows that is older than Windows 7, then you should absolutely upgrade. You are already putting your data at risk by using an out-of-date OS. Get with the program.

But if you are using Windows 7, Windows 8 is not a very compelling upgrade — unless you want to join the Windows ecosystem. If you have your sights set on a Surface tablet and/or a Windows phone, upgrading to Windows 8 should be a no-brainer.

In the end, though, I think Windows 8 is similar to Vista. Not in the sense of being a crappy version of Windows, but in the sense of being a transitional version of Windows. I think I can see where Microsoft wants to take Windows, and I think it is onto something. But the direction Microsoft wants to go will require buy-in from the developer community. Traditional software and apps will need to merge — or at least cooperate — in a way they don’t currently. So while Windows 8 looks good, I think it mainly serves as a signpost pointing the way to Windows 9.