For months now, many of us have been pitting the iPhone against some other device.

In my case, I’ve staged gedanken challenges between the iPhone and various BlackBerry offerings from RIM.

With the iPhone finally being launched later today (June 29, 2007), we’ll soon have an opportunity to collect some real data to quantify its introduction and progress.

Of course, it’ll be interesting to see how various markets, market segments, etc., respond to the iPhone.

It’ll be even more interesting, however, to monitor metrics that quantify the overall size of the market, market segment, etc.

Market share quantifies (via a relative percentage) how the pie is sliced.

Market size, however, quantifies in absolute terms (e.g., monetary), how big the pie is.

Size matters.

And that’s why, to some extent, it’s not surprising to hear Apple competitors (many of them incumbents in the marketplace) welcoming the release of the iPhone. In other words, they may concede (especially in the short term) market share to the iPhone. However at the same time as the market itself grows, these Apple competitors may also experience growth.

[Update: Are there any early indicators? Perhaps. On the eve of the iPhone release, RIM made a number of powerful announcements. Their profits are soaring, their stock is splitting and they’ve introduced a new product. Not a bad way to capitalize on Apple’s marketing tsunami around the iPhone! (And who said it was a marketing faux pas to make press releases late in the week!)]

At least in this respect, the iPhone certainly does appear to have the opportunity to drive the handheld market.

And that could make matters quite interesting!