does anyone use the tire belts to prevent punctures
how effective are they
When I lived in the Mojave Desert area of So Calif, I had to deal with goatheads amoung a bunch of other natural and manmade trash, but found that goatheads penetrated Mr Tuffys every once in awhile. Other wise they work ok, but you have to use a thick tube or sand the liners edges down because the edge of the liner will wear a hole in normal tubes.
If flats are bothering you then your first line of defense should be the tire not the tube or a liner. Specialized makes a tire called the Armadillo that goatheads didn't even penetrate and I use ultralight racing tubes and no liners. TheArmadillo is probably the most flat resistent tire on the market not only in the tread but also in the sidewall, but it is heavy at about 375 grms. Specialized has came out with a new Armadillo called the Elite which promises to have the same level of protection as the regular Armadillo but far lighter.
Keep in mind, even thought the regular Armadillo is heavy, if you were to pursue trying to get a lighter tire more puncture resistent by adding liners and heavier tubes you would be dealing with close to the same weight per tire anyways. Here's how; take an average road tire that weighs 230grms add a 100grm regular tube then add 100grms for the liner that equals 430grms; now take the regular Armadillo at 375 add an ultralight 65grm tube and your at 440 grams but have better flat protection and longer wearing tire.
Stay away from Slime tubes for road bikes, they will not seal a leak once you attempt to air up pass 65psi; at which point the green slime just blows out of any size hole making a mess inside your tires and rims and rim tape; plus their heavy at about 120grms for the racing version, and they use a cheap crappy presta valve that break in short order.
MR tuffy works for me. No flats even on a ratty tire. If not installed correclty they can cause flats, they reduce efficiency of the bicycle. Consider picking class out of your tire every 5mi-10mi with a knife. Mr Tuffy stops the glass but it is still embedded in the tire slashing it up.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.