The Palm handheld organizers have justly been touted as brilliant devices, but they've lacked one feature: competition. As a result, the pace of innovation--and price cuts--has slowed recently.

Palm gained an effective rival this week (as opposed to the slower, larger, poor-selling "palm-sized PCs" running Microsoft's Windows CE operating system) from an expected, but still uncomfortable, source: Palm's original founders. They left the company last year to form Handspring Inc., which on Tuesday rolled out its version of the popular handheld, the Visor. Hype alert: This rollout is mainly ceremonial, since supply limits mean Handspring won't actually ship anything to customers until October and will sell the Visor only through its Web site this year.

Most of the Visor's features look familiar and unremarkable, since Handspring uses the Palm operating system. The basic Visor is roughly the size and shape of earlier Palm devices, with the same high-contrast screen and pair of AAA batteries on board, but it's done up in black with silver-tone buttons. The built-in programs are also mostly identical, with the addition of a beefed-up date book (it integrates your to-do list and lets you keep a daily journal), a world clock and a calculator that can tackle math, trig, finance and statistical calculations and do conversions. The desktop synchronization software is the same as before, although Handspring includes the Mac desktop tools instead of requiring users to download them or buy an extra CD-ROM as Palm does.

The Visor offers four key advantages over the Palm line. It's cheaper: The base model, with 2 megabytes of memory, sells for $179, while the 8-meg Visor Deluxe, in any of five colors, goes for $249--cheaper at its list price than the discount price for the Palm IIIx, which has half the memory. (The base model is also available without a syncing cradle for $149.) It connects not via a serial port but the far faster universal serial bus, so data can flow into a computer much faster--and can flow into an iMac without requiring clunky cable adapters. (Handspring will sell a serial cradle for use on older computers and with the USB-challenged Win 95). It has a built-in microphone--although it's of no use until other developers provide software to enable it. And it pioneers a new open-ended Springboard expansion slot that will allow third-party developers to expand its utility in all sorts of interesting directions.

That Springboard slot is the most significant change, greatly boosting the viability and flexibility of the Palm genre by allowing the device to change, chameleon-like, with a swap of expansion cards. There are only a few cards to demonstrate the potential this hardware enhancement now--so far Handspring is offering a 33.6 Kbps modem, a backup card, a memory-expansion card and a plug-in cartridge of a Tiger Woods golf game from EA Sports--but the slot design offers more fascinating possibilities. These cards plug into the top of the rear of a Visor, leaving room for extra hardware--say, earpieces, antennas or extra batteries--to protrude outside the unit.

And so on the hardware side, we're promised pager modules, digital music players, a Global Positioning System add-in, a wireless modem and, yes, a wireless phone. On the software side, the sky's the limit--anything that can be designed to work within the Palm OS and can fit into a read-only memory chip can be added to the Visor. And since Handspring's management is the folks who brought you the original PalmPilot, there's cachet attached to the Visor now--an important consideration in this style-conscious field--as well as promise for an interesting future.

Visor, Handspring; Win 98/Mac, $179 ($149 without cradle). Visor Deluxe, $249. http://www.handspring.com.

CAPTION: Expansion-minded: The Visor hides a "Springboard" add-in slot.