Bearing in mind I may ignore you all when I get home and see what Fowler's says, what's the general feeling on using 'a'/'an' before acronyms and initialisms? Would you rather treat the abbreviation as a pronounceable word (i.e. 'an RSS feed', since 'R' begins with a vowel sound) or do you like to consider the words that are represented ('a RSS feed' because 'Really' begins with a consonant sound)?

Or do you just use the same each time regardless?