I wonder if sales of these devices are slow in part because of the OS it runs on. Everything cool in mobile seems to be either Android or iOS. If developers don't do webOS, there aren't going to be killer apps for it. And apps sell devices.
Browser, email, maps, media player are the killer apps, and every device has them. I think games is the downfall of some devices.
Blackberry Playbook not having an email client, that I would call an app that would prevent a sale, but does anybody really look at the app catalog and say to themselves "if it hasn't got angry birds, I'm not buying it"?
I've played with webOS, and I wasn't wowed, but anybody I know who as owned a webOS device (and has had both Android and iOS) are adamant that it is the best OS experience out there.
You simply can't bring a competing platform against the ipad and not compete on price if you don't have anything else to offer.