HP has come to the rescue of struggling Palm - but I think it's doomed anyways. Sure, WebOS is a fine accomplishment. In the year+ since the original WebOS device (the Pre) was announced the OS has matured nicely. And if the Pre had come out in early 2008 instead of mid 2009 Palm would probably be riding high again. Problem is, Apple and RIM had already gobbled up all the mindshare for smartphones (enough to convince Microsoft to reboot their platform entirely) and there was nothing left. Plus, when Palm introduced the Pre it was a US-only CDMA device and was only on the smallest CDMA carrier.
Since then, they've broadened the line of WebOS devices but it's too little, too late. In buying Palm, HP gets WebOS - a nice hedge against Android and Apple that lets HP come back into the mobile space and with an OS they control. And WebOS in theory should scale nicely for tablets and other cloud-based devices.
The catch is that HP has never shown any ability to market mobile devices. They have also never really had an aptitude for mass marketing outside of their printers. HP is pretty much a consumables and services company right now. They have more market share than Dell right now, but that's mainly a function of Dell's ineptitude more than HP's prowess. Someone has to be the market leader.
Fortunately, HP is big enough and profitable enough to keep a Zombie Palm running for a long time to come, enhancing WebOS enough to keep it competitive but never a major player in the market. I don't see them ever leveraging Palm into a major market share play. That ship sailed a long time ago and I think Android was the last entrant into the market.
My last Palm was a Treo 700p - which I ditched in favor of an iPhone the day the iPhone came out 3 years ago and I haven't looked back since.