On year 5 using a cassette toilet where we boondock/dry camp almost exclusively. The positives are that it allows you to be out in the boonies longer even though the holding tank (cassette)is generally much smaller than a regular RV black water tank.
This forces us to use less water. Besides being able to dump the portable cassette tank in any number of sewer facilities, another real plus is when there is a sani dump at a government campground and there is a long line of RV's waiting to dump and some take up to 10 minutes or more to get rid of grey,black water and fill with fresh, you can park close by, carry cassette to the drain, soon as RV has pulled their hose and are stowing it, dump cassette tank which takes 10 seconds, quick spray and then return with out interrupting anyone in the line up.
Dave