Transfers that are worth doing are the exception rather than the rule. Transfers from airlines that participate in HHonors Exchange (except for AA, which has a lower exchange rate) to Hilton are a pretty good deal, but transferring from HHonors to airlines is not.

Another worthwhile one that has been available for the past several years is AA and UA to Diners Club and then to British Airways at basically a 1:1 rate (though there will now be a service fee on that).

Most other transfers are a waste and it's usually a better option to try and top an account up to an award level then lose a bunch of value moving points/miles between programs.