Yes,
Your 645 may seem fine now, but......ALL formats are great. Horses for courses. Youll still come back to 35mm but I know what you mean, small 120 cameras are the dogs.
I use 35mm, 645 and LF (with 120 backs (6x9). The large formats are sonderful to print but sometimes I cry out for the spontaneity and fun of the smaller formats and find it unusual to say "if only I had used a bigger format" as half the time it just does not matter from teh point of view that i the image looks great, it looks great and another format may have meant not being able to get light onto film.
I adore my Bronica RF645 and will eventually get round to posting some more shots when I return to the UK and can scan some.....but it cannot do close portaits on the move like my 35mm can.