Whether you know it or not, this has an actual effect on the ability of the project to spread by word of mouth (online or otherwise), therefore its success and number of contributors it'll get.
The Greek letter Mu is the SI prefix for "micro".
μTorrent seems to do fine with the Mu, even though most people write it as "uTorrent" and spell it as such.
You've said it yourself there; μTorrent was rebranded by the majority of users to uTorrent, and "uTorrent" is a distinct, mostly spelt-how-it-sounds and easily-Googleable name.
I doubt that an involuntary rebranding of μg to "ug" would be quite as successful, nor likely to happen.
Pronounced "MEE-KROG", right? First syllable rhymes with me, second frog.
I completely agree with you.
"What's that you're using?"
"Microgram, I think. It's cool, you should check it out"
sound of frantic typing
"I can't find it on Google, how do you spell it?"
Variants on the above conversation happen every day.
Adopting a name like μg only places petty and annoying barriers in front of potential users.
[1] http://www.kalzumeus.com/2014/04/09/what-heartbleed-can-teac...