Apple has basically killed off its competition with the iPad.
Look the HP Slate was announced a couple of weeks before the iPad. Than the ipad was announced. HP knows it had it's work cut out for them especially when Apple announced the $500 16GB ipad wifi model. HP and the other competitors were hoping Apple would be priced much higher and than people would buy the competition at the lower $400-500 prices.
Of course, the other issue is stability. Microsoft's Windows 7 is probably not that stable for slate computing. I agree Google Andoird or Chrome will be a viable alternative.
But again, the competition is so far behind. They saw what the iPad could do. Either they had something in the works, but when the iPad was announced, they had to go back to the drawing board.
Research and Development in the tech world for brand new products take at least 2 years. Look at the iPhone. It was announced in Jan 2007. Where was the competition. Google made beta users out of the first G1 buyers with Tmobile in Oct 2008. Google's Android system really wasn't stable until version 1.5/1.6. By than it's more than 2 years after the original iphone launch. Same thing with the Palm WebOS. It wasn't announced until after 2 years after the iPhone launch.
The competition is so far behind Apple at this point in development with the ipad. Sure it will eventually catch up. But how big of a lead with the iPad have by than.
In my opinion, a real competitor to the iPad won't be seen until at least 18-24 months from now (mainly because Google can use their preexisting Android OS or HP with the Palm WebOS).
That's why there's no competition right now. They are all back to the drawing board trying to design something that can undercut Apple's prices and still maintain healthy profit margins. At this point, it's not worth the risk to these companies. They are just letting Apple blaze a trail. The lead might be too big to overcome (see Sony Walkman vs. Apple iPod for historical perpective); and yes I know Apple wasn't the first MP3 player (I actually had one of the very first, the RIO Diamond MP3 player). Apple isn't the first with the tablet/slate but they are the first to successfully mass market it.