It seems to me (and in line with Canon's typical behavior) the EOS-M is intended to be a mediocre offering that simultaneously (and halfheartedly) gets them into this market segment and gives Canon some idea of how well it sells without hurting dSLR sales.
Keep in mind these classic moves by Canon- killing the Pro1, removing RAW from the S80, killing the G line after the G6, reintroducing the G line minus RAW with the G7, removing HD video from the G10 etc. This is a very conservative and very cautious company. Obviously, very reluctant to infringe upon their dSLR sales in any way.
My guess is that there were some serious internal battles about launching the EOS-M. Obviously, some design concessions were made to assuage the dSLR department and their accountants.
I for one am looking forward to buying a Canon mirrorless camera once they make a serious attempt at it.