The touch-based web browser feels like a missed opportunity. It's incredibly basic, but even the basics it doesn't quite get right. You see, TouchSmart PCs support multi-touch just like the iPhone, but it's criminally underused and fails to work in the one area where you really need it to. I'm referring to scrolling web-pages in the aforementioned browser. Using the side bars with a single finger is never a problem, but try to scroll anywhere onscreen using both fingers, and as often as not the browser takes your straight to the bottom of the page and refuses to let you scroll back up.
Meanwhile, the only other area where multi-touch is used is the rather pointless ability to zoom the upper row of tiles slightly on the home screen. The single biggest problem with TouchSmart though is how limited it is, and how quickly you find yourself needing to go back to Windows. Essentially, this is a PC which should be capable of so much, yet TouchSmart doesn't seem to offer much functionality beyond what you'd expect from a half-decent PMP.
Another area where HP really needs to get its act together is in providing a custom onscreen keyboard, rather than the small pathetic Windows default effort. The only saving grace here is that Microsoft's handwriting recognition works almost flawlessly on the IQ810. As a last point, HP sells a wall-mount for the IQ810, which makes the touchscreen nature even more useful.
The IQ810 doesn't stack up too badly as an all-in-one machine. Compared to the fairly similarly-priced Sony VGC-LV1S all-in-one, for example, the Sony might feature an HDMI-input and a faster CPU, but the HP wins out with out with a larger screen and hard drive, far better video card and of course touch functionality all for only £100 extra. Other options are Dell's XPS One and, of course, the Apple's 24in i-Mac. These two machines are a good hardware match in terms of value for money, so it really comes down to whether you want touchy Windows or not. The one thing to keep in mind here is that you might 'soon' be able to upgrade the HP to Microsoft's Windows 7, which is being built with touch interfacing in mind.
HP's TouchSmart IQ810 gives you 25.5in of touch-screen PC goodness. The TouchSmart interface is limited in its usability and still needs work, but then you're not paying that much of a premium for it.