I'm still undecided. Took my bike out for a quick ride around the 'hood the first day I bought it. Woke up the next day, flat tire. Got new tubes with slime, and started commuting to work 3 months ago, no flats. Have had difficulty airing up tires once in a while though due to the slime I think. I'd probably go with either thorn-resistant tubes (here in AZ) or tire liners next time, but can't argue with the slime results.

And I should mention, just using cheap Giant tires that they sell on their bikes, nothing really tough.