Back again, and on with the theological debate. Boycey, dear sir, I'm sorry but I must refute much of what you say:
"good quality bag makes it no problem. pac courier bags have 4 way straps that hold everything to you, no bouncing. a cheaper alternative is the ortlieb messenger bag, i can happily carry 24 cans in that
furthermore, i fucking hate panniers! i know there can't be that much difference with carrying the weight on your body but it feels like some kind of horrible ball and chain unbalancing the bike, making it wider and changing the centre of gravity to position that makes the bike harder to control... and ruining the smooth lines my sweet bicycle"
Chap, dear chap. Surely you're not really arguing that strapping 24 cans of beer to your back is going to be as comfortable as racked on your bike? Also, surely you're not really claiming that equally dividing the weight low down on each side of the wheel affects your handling as much as that sort of weight high up? You've raised your centre of gravity, you've made yourself personally far less balanced - these are far greater hits to handling. Consider also that each time you lift out of the saddle, you're lifting that weight too, so cranking up a hill becomes far more work. As for lines, well see above. The looks of a commute bike are a very, very low priority consideration, in fact from a theft point of view the uglier the better.
"none of what you describe is any problem whatsoever on a steel road/track bike. a little bit of bike handling skill goes a long way. i couriered for 4 years on a steel road bike carrying VAST packages up to 300 miles a week on london roads, no trips to casualty, i damaged 2 frames in that time: 1 was hit by a van while i was eating in a restaurant, the other failed due to crash damage from it's previous owner."
I'm deeply happy to hear that you've yet to have a crash, and wish you the best of luck in continuing that streak. Unfortunately my own run is not quite so lucky, but such is life. Either way, are you really claiming that as a cyclist the safest thing you can do is not keep a straight path, but veer around for road obstacles? I really do think that would be a very questionable assertion. Or are you claiming that the road hazards I've described - bumps, bike paths that hop onto pavements, potholes, steps, etc - don't feature as part of your commute. If that's the case, then I'm rather envious.
"good quality steel frames have a lifetime up to and beyond 30 years, aluminium is 10 tops. look out for cracks. the rust only comes into play if you store outside."
Again, this is a commute bike. It's going to get scuffed and scratched, and it will be stored outside I'd have thought. If that's not the case, again I have to respond with envy. I lock my bike to bike racks outside my office, where other people scrape their bikes against mine. It gets locked to street furniture outside shops, gyms and pubs. How else do you use your bike if it's for general commuting.
Now it's absolutely correct that aluminium does not have infinite fatigue life. However, your 10 year claim is very, very inaccurate. The marin parked outside my office right now is older than that, the second mtb I ever brought. It had a good 4 years of hard offroad life before being retired to commute life. , which it's been doing faithfully for many years.
"Lemon Eddy, i say this as a reformed "slick tyred mtb ftw" type. don't knock it till you try it"
Somewhat presumptious to think I've not got experience of big wheeled commuting too, and rather wrong too, I'm afraid. In terms of recreational hours, I probably spend as much time on my roadbike as my mtb. My first commute bike (and by god are we going back, we're talking the 80s and a Sun Solo) was a road bike, as were my bikes for many years after. So, having tried it, am I allowed to knock it?
[edited a missing "not"]
yum. Lemon Eddy, i say this as a reformed "slick tyred mtb ftw" type. don't knock it till you try it, your concerns though understandable don't actually translate to reality. you would be very surprised if someone were to lend you a decent audax bike. 
