Mount adapter ring...

[bytch_mynickname]

is it ok to use these? I have a Rebel XT and am looking to buy a film camera too and am debatign whether to get another Canon EF or go with a Pentaz because of the lower cost of lenses.

I would like to go with the Pentax so I can have more versatility as I only have the kit lens and a 50mm 1.8 for the Rebel but on the other hand, I would like to get something that has interchangeable lenses.

Anyhow, I came across this on ebay.
Is it safe to use? Advantages, Disadvantages? Would you do it? Anything else I need to know?

Thanks