Silnylon is lighter and stronger than older coated nylons and polyester fabrics, not as light as the exotics like DCF. Handy that it can be wiped dry with a backpack towel so that you don't have to pack up a wet tent. Seams need to be sealed with Gear Aid silicon sealant. Gear Aid also makes silnylon patches and other repair patches and tapes for other fabric types. Tenacious Tape gearaid.com
Traditional polyurethane coated fabrics used for rain gear eventually wet through. Some quicker than others.