Folks, have you generally had any luck with LNF claims for hotels in Europe, Asia etc?

I recently submitted some claims which were all shot down with the 'voucher' argument, though none of the comparison sites actually use a voucher of any kind.

May we please have a list (perhaps even a wiki) of sites that are commonly rejected by Marrriott LNF staff ?

So what sites have you tried unsuccessfully? Listing these sites will help others avoid wasting their time on submitting claims that will be stillborn.

Conversely, what sites have worked and pass their criteria?