Got mine from Mr Ultraseal at the Horizons Meeting in June :)

Love the Stuff

I've been using Slime, Goop and the like in my trail bikes for years now and (touching wood as I type) have yet to have a puncture.
Which means I suppose that it probably works, but I don't actually know for sure.

A bit of a digression - for which I apologise - but here in the UK they now sell bicycle inner tubes pre-filled with a slime-like puncture sealant.

A tyre company also states that this stuff puts weight where you dont want it, affecting steering etc. Cant remember their name.

I used it till I changed a tube and found 2 old patches peeling away, though the stuff had sealed it. A tyre fitter I know wont use it.

So Im unsure either way.

I've heard that some folk only use the stuff in the rear tyres because of this handling doubt and I've also read that most punctures are in the rear wheel anyway.
PS I have no way of knowing if the latter comment is true before people start replying with "I've had 17 punctures in my biking life and 12 of them have been in the front tyre so you're talking garbage...."