Some feel that the only reason Ford did the teflon coating was so that Ford would not have to pay for cleaning as a warranty issue. The throttle body does not gunk up as bad as the non teflon coated ones, but they still gunk up as you have observed.
Yes, you should clean it. Yes, you should be a little gentle when cleaning so that you do not destroy the teflon coating and the benefit it provides.
Even before the teflon throttle bodies came into use, Ford started to use DRI (deposit resistant injectors). In a similar manner, the injectors did not plug up as bad, but they still become somewhat restricted with time. Although not as critical as in the 80's, injectors still benefit from ocassional cleaning.
