I don't think you would save much weight. You should run lighter tubes if that's your concern. However, if you're looking to reduce flats you chould check out the Slime tubeless system. I know a few people who run it with good luck and it's pretty cheap. I would run it over Stan's any day.
Compared to a lightweight tube, it is a complete wash. Lightweight tubes are going to run 90-120g and the NoTubes rim strip is 54g and we recommend 60g of sealant. If you are using inexpensive tubes, the weight could be as much as 250g. As sanjuro mentioned, the reason to switch is not based solely on weight, it is all about performance and puncture protection.
To the best of my knowledge, Slime does not offer anything that compares in weight or performance and their sealant is much more expensive.
I'm a bit biased for good reason. Feel free to ask any NoTubes questions you may have though or you can e-mail me through the enquiry at NoTubes.com.
You should also know that we typically do not recommend Panaracer tires although many people are happy with them. A different style of folding bead construction makes them more likely to come off of the rims when inflated tubeless.
i've been running specialized fast traks with stans with some mixed feedback. I put a cut in the sidewall about 1 cm long, which flatted the tired in minutes, I run it with a tube on my non racebike now. The big thing is its a bit more work then a tube setup, but I completed my race season without a flat. I've heard its suppose to reduce rolling resistance as you eliminate the tube as well. As for less expensive, the kit is pricey (atleast in N.S. Canada)
Rolling resistance and traction are the reasons to go tubeless for sure. When I switched my xc bike to tubeless, those qualities were noticibly improved. It's really dry and dusty where I live so having a tire conform to the terrain and really use it's tread is a big benefit.
I've run pretty much every combination of tubeless rims/tires and non tubeless rims/tires all with sealant and using the ust rims AND tires is the best system.....with some goo for punctures.
PEOPLE SAY IT IS EASY TO USE AND LAST. however you might want to check out ghetto tubless some guys at the lbs told me about it and one of my friends got it works jsut as well and is easy to do yourself i think there is a review about it on www.nsmb.com but not sure. however if you do not like the idea of ghetto tubless i ssay stick with stanz that thing is awsome
plus i think they did test in which the stuck nells in it everywhere and it stayed together and sealed like nothing happened.