I have a slightly different take on fifty/50s as well as DoNs than your typical player.  Most casual players only play 1 or 2 tables at once, so as to maximize concentration on the table and better your read on the players at your table.  However, as micro limits are generally donk-filled (and therefore not too stimulating), I find myself often 4 or 6-tabling these games.  Because of this, profit per hour is maximized however profit per game is marginalized and the increase in rake becomes much more important.

If you are playing one table a time, I will admit the fifty/50s rake isn't quite so detrimental to your profits, particularly at the (rather easy) micro limits.  I played a single table fifty/50 today and won a nice chunk due to my aggression and some well-timed luck.

If you are using the fifty/50s to build up a micro-sized bankroll, or as an exercise in well-timed aggression, you will certainly achieve these.  However, if you are planning on plain old multitabling, DoNs or regular 9-man SnGs are the way to go.