Our reader “U-photo” made this useful size comparison between the 12-40mm PRO lens and the next PRO 40-150mm f/2.8 zoom. Big, but still less huge than f/2.8 tele zooms like the [shoplink 44875 ebay]Sigma 120-300mm f/2.8 (FF) lens[/shoplink].
P.S.: A new E-M1 review has been posted at Danielkcheung.com.