The PlanOn PrintStik PS910 portable printer is remarkably small, considering that it can print full letter-size pages. It measures just 1 inch thick by 2 inches tall by and carries 11 inches long (the same length as a sheet of letter paper). PlanOn designed this 1.5-pound unit for printing on the road from a laptop, a smart phone, or a PDA.

In its quest for portability, however, PrintStik may sacrifice too much functionality to appeal to more than a few users.

The PrintStik uses heat to print on a roll of thermal paper. Though this design decision keeps the mechanism small and simple, the resulting monochrome-only prints look like output from an old-fashioned fax machine. Text is fuzzy and uneven; and even at the highest quality setting, images appear as pixelated patterns of dots. Moreover, the pages curl up the way thermal-printed credit-card receipts do, and tearing the sheet from the printer leaves a rough edge.

The paper comes in a cartridge that fits completely within the printer, but I found the cartridge awkward to install. Each cartridge contains enough paper to print 20 pages; a packet of three cartridges costs US$25 (about £14). PlanOn also sells economy packs of nine cartridges for $60 (£33), lowering a per-page cost -- still considerably more expensive than most laser printers and inkjets. Two upsides: The printer imposes no additional ink costs, and only the amount of paper you need scrolls out when you're printing a partial page, so you don't waste any.

Currently, the PrintStik works only with Windows computers and BlackBerry phones. PlanOn plans to announce drivers for additional phones and PDAs as they become available. The printer comes with a handy retractable USB cable, which also charges the built-in lithium-ion battery as an alternative to the included wall charger. I had no trouble printing over USB from my Windows laptop.

Printing via Bluetooth from a BlackBerry Curve 8330 was more troublesome. Though the Bluetooth pairing went smoothly, the print driver didn't seem quite ready for prime time. It adds a print item to several of the Blackberry's menus, which let me perform simple tasks like printing appointments, tasks, and memos. But print support was missing from complex applications, such as the Blackberry's built-in Web browser.

To print photos shot with the Blackberry's camera, you must save the image, use the included File Browser to locate the file, and then select the print function. I tried adjusting the print settings, but never succeeded in printing an image this way -- the phone paused for a moment, but nothing printed. That's a shame, because the combination of the phone's camera and the PrintStik could be useful for rough-and-ready photocopies.

The PrintStik is useful for quick PC printouts on the road, such as draft documents for mark-up, rough price quotes for customers, or driving directions to your next appointment. It also makes a good companion to a PlanOn DocuPen portable scanner for making quick copies. But the PrintStik's poor print quality makes its $300 (£168) price seem too high. For less money, you can buy a Canon Pixma iP100 or an HP OfficeJet H470 -- portable printers that are larger and heavier than the PrintStik but also produce desktop-quality color prints.

UK release dates to be announced.