Belts with good tread will break the track up enough that the row unit works pretty much like normal.  Belts with little tread seem to roll it down harder and you have trouble with penetration.  The same thing happens with tires. 

I won't say "there's nothing to worry about" because sometimes there is, but we have planted for quite a few years behind the tracks of our 35 with only occasional problems.  After we started running two planters, we would just keep it out of fields with a lot of clay if they were a little wet, and plant them with the other tractor which ran between the rows.  This year, we have set the 35 up on 120" so it is running between the rows.  It will be nice to not have to worry about which tractor is where, although we still will because of refuge and because the track  and 24 row is able to handle far wetter conditions then the mfwd with the heavy 16/31 split row behind it.