HP has highlighted several features that it hopes will set the TouchPad apart from rivals, including wireless charging, touch-based document sharing, and tight integration of Twitter and Facebook capabilities. It also supports Adobe Flash, unlike the iPad but the same as most Android tablets.

TouchPad sales won't match those of the iPad 2 and it's hard to say how many buyers will be drawn to this first incarnation of the device, Epps said. In a survey of people considering a tablet purchase conducted by Forrester Research in May and June, 7 percent were considering a TouchPad, compared to more than 50 percent for the iPad 2. Just under 30 percent said they were undecided.

In some respects, such as weight, the TouchPad is more comparable to the original iPad than the iPad 2, which won't help with adoption, Epps said. But this first release gives HP an opportunity to gauge market response and hone its device.

It also expands the ecosystem for webOS, which is already in some smartphones and will go into printers and PCs in the future. That's been a big part of HP's selling point: It promises that webOS devices will be tightly integrated to enable easy sharing of documents, contacts and other data.

Several TouchPad buyers interviewed Friday were either gadget enthusiasts or developers, and already owned iPad or Android devices. They were curious to see how webOS would perform, and some were looking for an alternative to the status quo.