Windows 7 has ONLY surpassed OS X in terms of ownership & shipping volume, along with updates for real world user volume statistics. Where have you been?! The HP Slate is a dead mission! Its not going to be released - too underpowered for full Win7, a rumored rewrite to using WebOS (which is a smarter move), and heavier weight to it not being produced at all.
Right now I've read 3 potential iPad fighters being shelved - even Lenovo's netbook/tablet hybrid a sexy idea is being shelved!!!
All the others where VERY slow to marketing, shipping REAL end products with backing by publishers, mobile video content development houses, and real world useful apps for them that they're now dying before even passing marketing department before production.
YES there were MANY Tablets "slate" models on the market and still are. They're very sparse in wide acceptance. MIDs right now have a MUCH better chance; and those WinCE tablets that stock brokers used on a shoulder leash in the NYSE or NIKKEI are ancient and serve a specific purpose that "MAY" get shelved. They're better seen as MIDs just like the HTC models from 2yrs ago and the Dell model that O2 is getting next month.