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Sealing
There were blobs of dense white dish-washing foam all around the tyre side walls though. The video (on the Notubes web site) points out that this is where air is escaping through the tyre. So to help these seal the tyre needs rotating and tipping, rotating and tipping. The object being to lap sealant on to the whole inner surface of the tyre and rim and crucially the valve stem bung. When this has been done for a few minutes (crowds of curious onlookers may gather so choose a quiet time at the petrol station) the tubeless tyre is ready to roll. The instructions advise going for a ride straight away, some instructions are less of a chore aren't they? I went for a quick hours blast and the tyre held up perfectly.

Follow up
By the end of the following day sitting in the garage the tyre had lost around half it's pressure. I did some more rotating and tipping and used my track pump to top it back up to about 45psi. twenty four hours later and the tyre had only lost 5psi. So things are looking good and the tyre is going to get a total hammering at Afan Argoed on the 9feet trail. We'll do two complete laps and throw in the infamous MTB Britain extreme detour to round things out. If the tyre (front) can stand up to that I'll do the rear as well.

The two rolls of tape supplied are enough for four wheels

Note: it is possible to run UST tubeless tyres on a wheel set up with Stan's system.

Details as tested
Rim: Mavic X517 36 hole on XT hub.
Tyre: Specialized 2.0 Team Control Team Edition (Kevlar bead).
Valve stem (supplied with kit) Presta type.
Initial riding pressure 40psi.

Advantages over inner tubes
Thorny punctures self healing.
Pinch punctures reduced/eliminated.
Lower weight.
Lower rolling resistance.
Better grip if run at lower pressure (beware rim damage on rocks).

Advantages over other tubeless
Cheaper wheels.
Cheaper tyres (remember replacing your tyres regularly is the key to good traction).
Use standard tyres with your choice of tread.
Lower weight (a good tubeless tyre weighs more than a standard tyre by around the weight of a standard tube ' 180g). Stan's sealant and valve stem weigh 75g so the system is about 100g lighter than tubes or Mavic UST. This is half a pound off your wheelset.
Punctures self sealing.
Less air leakage - UST can leak around 7psi per day.
Doesn't need special tools to true on the trail.
Doesn't need pumping up to high pressure to seat bead after trail fix.

Disadvantages compared to inner tubes
More expensive (probably not over time if you puncture with inner tubes).
More work in initial set up.
Needs high pressure air/CO2 for initial inflation (not a track pump).
Trail fix requires unscrewing valve stem (not much hassle).

Disadvantages compared to other tubeless
More work in initial set up.
Needs high pressure air/CO2 for initial inflation.

Summary
Stan's tubeless system is the best of the alternatives if you're prepared to put in the set up work. If you're lazy stump up the cash for Mavic's UST and just try and patch the inside of the tyre when you get holes (an inner tube can be used as a quick fix on the trail with UST too)' 

Resources
Stan's Tubeless Website

Tubeless Tyres ...the different systems explained

Follow up long term review
We gave the front wheel set up as above (note this is NOT a tubeless tyre, it's a standard Kevlar tyre sealed with Stan's sealant) a really good thrashing at Afan Argoed on Sunday the 7th July 2001. We rode two full laps of the 9Feet trail then threw in two additional loops to repeat first, the whole of Desolation and the Hidden Valley, then another loop to repeat the amazing Dead Sheep Gully. The tyre lost no air, felt lighter and seemed to give better grip than normal. I put the additional grip down to running the tyre at 40psi - 5 pounds lower than my standard pressure.

In case you think we didn't hammer hard enough, we timed runs as follows:
Hidden Valley 4 minutes 26 seconds.
Dead Sheep Gully 2 minutes 36 seconds.

Check it out yourself to see if you can beat them!

Friday 13th July
The tyre has lost no air. We expected some air loss over time but it's holding as well as a butyl inner tube. I'm taken aback by the effectiveness of this system.