lypsyl wrote:

£4 is worth it not to have to get your fingers dirty

You will still have to check the pressures every week regardless of the gas used to fill the tyres, as this is and always has been sound car maintainance.
Removing the valve cap to check pressures will get your fingers dirty, regardless of whether you then need to reinflate.
I check my pressures every week and on the FL2 do not need to top up more than 2 lbs/sq inch every 4 or 5 months.
Nitrogen from a cylinder is dry as compared to atmospheric air but then the outside of the tyres is constantly bathed in wet air, admittedly at a lower pressure than the inside of the tyre.
One pound a tyre is not exactly over the top, but since checking the pressures results in a small escape of gas you will over time still need to add gas and that would have to be done at a Nitrogen supplying outlet.

You can get a desicant (sp?) dryer to attach to a compressor and there will be no moisture. The dryer would need changed more when you use the compressor more. I think it's based on silica gel like what comes in a package with electronics but it's more like a filter the air passes through. I carry a gun because I can't carry a cop.
Ted Kennedy's car has killed more people than my gun.

2008 Freelander2/LR2
-Rimini Red

2005 Freelander
-Bonatti Gray
-EBC front brake rotors
-DAP-Inc. Lift
-BFGoodrich All Terrain RWL
-Muffler Delete
-CAI

As was stated nitrogen has different characteristics than atmospheric air. Nitrogen molecules are also much larger than oxygen molecules which is why a nitrogen filled tire (tyre) holds its pressure much longer than atmospheric air. Its the holding of pressure that causes the tire to last longer (along with nitrogens ability to keep out moisture compared to air) and as we all know saves gas by having properly inflated tires. I am a believer in nitrogen because for the price i pay for tires and the little cost of nitrogen it just seems like good insurance to make those tires last a little longer and in the long run actually save a little money.

I go off road a fair bit and let the tyres down for better traction so no good for me

Most Major earthmoving equipment manufactureres and, users, have been using dry nitrogen in their tyres for many years now. They do of course have the ability to purchase and store the necessory quantities required for the inevitable punctures unlike us fl2 owners.
It has been proved many times over that dry nitrogen prevents internal tyre degradation for the various reasons in all your posts. This prevents a tyre failure developing from the inside and thus saving a lot of expenditure.
On a personal note, I cannot see the justification as A- the tyre has to be filled from first installation and B- the first time you have to top it up with "normal" air, because your miles from any Nitrogen, you have effectively destroyed all the good work of the Nitrogen.