my personal preference... mBTC to be refered to as "bit" or "bits" rolls off the tounge really easy if you say it.... "That'l be 2 bits please"
That's kinda cool and has an "Olde Tyme" ring to it because two bits used to mean a quarter. "Shave and a haircut......two bit!" It harks back to a time when currencies didn't get debased and may help draw in the older crown who are losing their retirement funds to inflation.
The only drawback is that it doesn't have a unique meaning. "Bitcoin" can only refer to Bitcoin, but "bit" can refer to a lot of things. This is disadvantageous in terms of search engines, keyword analysis, and other things, as well as being ambiguous in some situations.
Not sure the ambiguity would be that big of an issue.. a lot of words have multiple meanings.. we seem to get along just fine.