I don't want to be seen as perpetuating the debate, but I'm in a similar dilemma (G v M). So I did the side-by-side thing at the Apple Store in London for about an hour.
(if you want to do the same, try upstairs - you'll never get two MBPs to yourself downstairs because of all the punters reading their Hotmail accounts - they're virtually queueing up to use them. Someone even came up and started to use my iBook which I'd got out and placed alongside a matte MBP
)
I did a display calibration on two adjacent 15" C2D MBPs, one gloss, one matte, made sure brightness was up full, then ran FinalCut Pro on both, the same project, the same window layout. Here's what I thought.
* Yes, blacks appear slightly blacker on glossy, and the deeper blacks make dark scenes in video... well, a bit darker. Peak brightness is also slightly better - the menu bar on the glossy was clearly brighter than the matte one. A bit more like a flashlight! However, standing back and looking across the whole screen, it's not as if the glossy was dramatically brighter. Not that much in it.
* Colour rendering seems much the same. Like someone else said, don't confuse "saturation" with "dynamic range". Photos look a little snappier on gloss (which is quite nice) that's all.
* The glossy had always looked to me as if the colours and brightness vary more depending on viewing angle. I spent a couple of weeks with a glossy 15" MBP recently and often felt that the display brightness was a bit uneven compared to my trusty iBook - it seemed like a band across the middle of the screen was always brighter than the top or bottom. But I think that's simply because the top of the screen is at a different angle relative to your eyes than the bottom of the screen. However, when you play with the matte, you realise that the screen's apparent "gamma" and colour rendering varies with viewing angle just as much as the glossy. I wouldn't say that either is going to be particularly accurate for photo editing as what you see is very much dependent on viewing angle, especially in the vertical direction. Both are perfectly usable, but if you need accurate, repeatable colour, connect an external display.
* Glare and reflections - here's my interpretation. Lights that happen to be behind the user reflect in both displays. The difference is that the matte reflects light as a broad "wash" which reduces the contrast over a significant portion of the screen. However, it doesn't reduce the contrast so much that things become illegible (and probably won't until you shine something very bright at it). When you come to the glossy, the same light produces more of a "specular" reflection, and therefore has an effect on a much smaller area of screen - most of the screen's appearance is unchanged, but where the reflection occurs, the reflection is so bright that it often makes text in that small part of the screen unreadable. Solved by moving your head a bit or changing the screen angle. The question is, on the occasions when it's an issue, do you want to have to keep moving your head to see a particular part of the display?
* Comfort level. It's kind of subjective (and after an hour of staring intently at one machine then the other, my eyes were going a bit woozy on both!) but I came away feeling that if I had to sit and work for two hours on either machine, I'd be a bit more comfortable doing it with the matte display. Perhaps this is due to the effect mentioned above... was I subconsciously moving my head around to be able to see portions of the screen?
I must say, it was a very close run thing between the two, and after an hour I still couldn't honestly tell you which I preferred. Both of them are great, there wasn't nearly as much to choose between them as I thought there would be. I wish I could have played with them in an averagely lit room, and a darkened room, as well as the uber-bright environment of the Apple Store.
The glossy is obviously excellent for watching DVDs, and will work better outdoors (which might be a factor for photographers like me who occasionally have to literally work "in the field"). But I got the feeling that 95% of the time, my eyes would be happier working for extended periods on the matte. And that's what might have clinched it.
And yes, the matte is WAY better looking that the screen on my old iBook - it must be twice the brightness. The iBook was near-illegible in comparison with the matte MBP. Yet I'm pretty comfy using my iBook indoors in anything other than direct sunlight. So I'm sure I'd be extremely happy with the matte.
In truth, I'm sure I'd be pretty happy with either. If pushed, I think I'm leaning towards matte - which surprised me. Then again, ask me tomorrow and I'll probably tell you something different. Ugh, decisions decisions... I almost think Apple would do better to give us no choice at all! How many sales are they losing because people just can't make up their minds?
I'd still recommend that you check them out for yourself, but I hope my comments are some help to fellow ditherers.
P