I'm not sure that is entirely fair, as certainly when Vista was new everyone was steering well clear of 64-bit due to fears, XP64 experiences and driver woes.
Of course over time, Vista 64 has bedded down, drivers become plentiful and people get experienced with it, making it (as far as i can tell) a useable OS that can be recommended (as much as Vista can be).
As to the O.P., can you tell any difference? I'm not convinced i'd ever advise anyone to upgrade from 2 to 3 Gig unless it was a 2 Gig stick with a spare slot for another cheap stick.
Let us know...