I'd agree, most users won't notice.
From a professionality point of view, I think the only person that will be judging you on your extensions is a fellow developer, I always take note of people's file extensions, and if i see someone with .asp or php extensions i always chuckle to myself know that they've worked 3 times as hard as me to produce the same result.
From a point of view of a general surfer, i really dont think they'll notice, although they'll automaticaly note all the variables listed after the file extension like ?id=37474&homedec=yes+no&thisiscool=yesiknow!4% and probably think, "ooh, that looks like amazon and hotmail" which may sway them into thinking you play ball with the big boys.
But I really dont think its an issue, use whatever you are more conformatable.
I know i dont have an issue with showing my .cfm extensions on my sites, the only time i would ever consider changing things over to .html is if i had massive datasets which were very slow to load or a massive resource drain, in that case you can parse the data on a daily basis into static html files and let you users surf those.
Rob