The general opinion is that WebOS is quite a good software platform (within the top 3 for smartphone platforms), but the hardware it's running on isn't the greatest. Some find the keys too slippery and hard to press, while others have suffered some build-quality issues. The main one being a wobbly slider - often nicknamed the "Oreo Effect." Also be wary of the bottom part of the slider as I know earlier revisions were very sharp - as in, cut a block of cheese as though it were a knife going through hot butter. I haven't heard whether devices shipping now have eliminated most/all of these issues, but it's still worth noting just in case.
Either way, the other big issue is the status of Palm itself. They are not doing too well at all financially at all. With the recent news that HTC walked away from a potential bid to buy them out, their future seems questionable at the moment.
I wouldn't go with it myself, but then I've pretty much decided I'm going to an Android device.