Re: Maybe So, Look at Macintosh
I thought they became acceptable when sufficiently much of what consumers use computers for had moved into the browser so that, with the native Microsoft Office also available, the software gap no longer mattered. Apple's transition to a competent OS in the years immediately preceding helped too. The switch to Intel was just the icing on the cake.
As for BlackBerry, I have to agree with the other commenters that a difference here is that Google probably isn't going to go on an anti-competitive market fixing spree. I also don't see how it matters that much to BlackBerry if people end up thinking of their OS as just a weird version of Android — from where they are now, anything that makes money is a win.