Ive used them and dont care for them. One or two ripped rendering them useless after like the second use. 2 gallon ziplock bags do a better job if you must go the plastic bag route and cost a fraction of the cost of space saver bags.
I'm completely sold on pack-it folders for travel. Campmor, who sells camping stuff, has them on closeout every once in a while. They're worth the investment.
CCL Inspiration 09
RCCL Explorer of the Seas Eastern 09
CCL Miracle Southern '08
RCCL Enchantment of the Seas Western '07
PCL Caribbean Princess Eastern '05
RCCL Explorer of the Seas Western '05
RCCL Explorer of the Seas Eastern '04
CCL Destiny Southern '01
CCL Sensation Eastern '94
CCL Ecstacy Western '92
CCL Jubilee Eastern '90