Let's take Handspring, for example. A year or so ago, there really wasn't much of a compelling reason to buy a Handspring Visor over a Palm device. Yes, there was the Springboard slot, but there weren't all that many modules. But the folks at Handspring did a gutsy thing: they designed the expansion slot and sold their products mostly (there was a bit of a price advantage for a while) on the promise of future expansion. I've recently spent some time with a Visor and a bunch of Springboard modules, and they're proving to be quite compelling. So the strategy of differentiating through a proprietary expansion slot is working for Handspring.

Ah, but I did say "proprietary." TRG also differentiates through an expansion slot. Their TRGpro supports a CompactFlash slot. This means, among other things, that you can put an IBM Microdrive (at http://www.storage.ibm.com/hardsoft/diskdrdl/micro/index.htm) into a Palm OS device and have up to a gigabyte of storage in your Palm OS device. Amazing.

But here's the thing: you can't use Good Technology's SoundsGood MP3 player (at http://www.good.com) in your TRGpro. And you can't use the IBM Microdrive in a Visor. And so while you can stick a gigabyte of music on your Palm OS device, you can either put it there (using the TRGpro) or play it (using the SoundsGood on a Visor), but not both.

OK, fine. It's reasonable for us, as consumers, to support the battle among these manufacturers to differentiate themselves based on the factors identified above. Will Sony's MemoryStick inspire a lot of add-ons beyond Sony's own memory upgrades and the little camera they recently showcased? Honestly, I don't know. But I'm beginning to doubt it.

That's because it's a challenge for hardware manufacturers to tool up and support a wide variety of platforms. The only way the TRGpro supports the IBM Microdrive is because the TRGpro supports a standard interface common across many different types of electronic equipment. But you're probably not going to see the eyemodule folks (they make the little add-on Springboard module camera at http://www.eyemodule.com) also support the Sony CLIE.

As a consumer, I can accept incompatibility and differentiation in this area. We consumers will vote with our checkbooks and certain add-on architectures will win (probably the Springboard) and some will lose.

That old syncing feeling
But there's another area of incompatibility with only limited differentiation that I just can't accept: the HotSync accessory interface. Every Palm device has a HotSync connector that allows it to be docked with a cradle. The cradle lets information flow smoothly between desktop computer and handheld.

This is an area where many Palm OS device users are investing quite a lot in add-on accessory hardware (often more than the handheld computer itself). For example, many of us have additional cradles (often at about $50 a piece), add-on keyboards (there goes another hundred bucks), travel chargers ($40 or so), a modem (cha-ching at $99), and more.