MIDs (Mobile Internet Devices) are being pushed by some notebook OEMs and silicon suppliers as the next big convergent handheld category. I've seen some presentations pitching the notion that they'll subsume smartphones, encroach on netbooks and UMPCs, and obsolete standalone GPS devices and media players.
There's no standard definition of a MID but the archetypes tend to be the Nokia N810, a long thin prototype device Intel's been showing, and according to some viewpoints, the iPhone. Most people think MIDs will have a 4-7 inch screen, a grade-A web experience, some form(s) of wireless connectivity, and plenty of memory and battery life. It'll probably have a lightweight OS of some sort (Linux, Android, Apple, some cut-down version of Windows etc), and is likely to have various consumer multimedia capabilities.
Many are quite likely to come bundled with some form of mobile broadband - either a familiar 'vanilla' operator Internet access, or perhaps a more under-the-hood wholesaled connection like an Amazon Kindle on steroids. Although the concept started as being quite WiMax-centric it has now evolved to 3G as well.
So far, so good. Basically a 2008-era PDA paradigm with connectivity built in and all the toys like GPS, right?
Maybe, but I'm less than convinced by the general-purpose MID concept. Anyone with a 6 inch device will have a normal phone as well (quite possibly a small smartphone itself), and their own or a shared family PC too.
Yes I'm sure there will be a few road warriors who want a day-trippable device rather than a laptop. Yes some teenagers with backpacks could have one instead of a PSP. If it's cool enough, the gadget fiends will be queueing outside the shops. But 100's of millions of units? Hmmm.
However.I can certainly buy into the idea that things like PSPs, TomToms, N810s, even iPod Touches could use some form of mobile connectivity. Not all of them, not all the time, maybe just for specific apps rather than general Internet services. Each category will adopt mobile at a different pace, and it will probably vary by country too.
Consistently, divergence has been more important than convergence for the last 10 years. For every two things that have combined, three new ones have emerged in their place - a consequence of Moore's Law and economies of scale.
So I see a small core market of converged general-purpose MIDs, really like mini web-optimised computers, bought as a 3rd or 4th device by urban techno-leaders. But that niche will be surrounded by a cloud of app-specific products, some wireless-enabled pseudo-MIDs, some WiFi only or remaining unconnected. Most of these will support decent browsers and extra secondary software clients too, but won't be optimised for them. Developers will face even more fragmentation than is the case for smartphones, but as the value for most of these products will be hardcoded 'out of the box' it won't matter too much.
For what it's worth, I'm still viewing the iPhone as a smartphone rather than a MID, as it can work as a primary phone and you don't look stupid holding it to your ear. (Its size is on the lower limit of MIDs, though, so I won't argue if you define it differently as part of the category - it's only semantics). Some of the larger WinMob devices, however, clearly fall into MID-land, which means WinMob7 will need to seriously step up the pace if Microsoft wants a role outside enterprise-type mobile products.
Overall - I'm cautiously optimistic about MIDs, but I see it as a fragmented movement towards enabling "mobile broadband computing" in a variety of different devices, rather than the genesis of a new generic computing segment.