After a remake of an old Veto loader i bought (it was a cracked piece of junk, but the cylinders were good) i also converted it to self levelling.
I find it much easier to work with, when handling bales with a grab, or pallets with the forks or straw with the spikes.
It also gives a 20% increase in lift capacity with the same cylinder force, because the self levelling dumps the center of gravity of the bucket down a bit during lifting. The self levelling makes that the lifting force on the bucket pin, is the same at any distance from the forks. Without it, the bucket swings up with the loader booms, which means that the lift force reduces when the center of gravity moves further to the ends of the forks.
I used mine for a few months before i changed it to self levelling, and it was a great way to increase lift force without sacrificing speed.
When it comes to handling jobs, i wouldnt want to do without it.