If your on the gas into/through the corner it will stay locked, if you let off before the corner it will ratchet until hit the gas again and then will be locked again. This goes for any lunch box style locker not just Spartans. I'd run a spartan over any of the others.
I have had Spartan lockers front and rear on my 2500 Ram for 2+ years. I have had Lockrites and Aussies on other vehicles and I will say that my experience is that the Spartan is the noisiest of the bunch. However, I have had zero problems with them during two years of hard use in a 7,000 lb rig!
I had a spartan in my toyota for almost 3years and probably 80,000 road miles plus hard wheelin on 37s, the cross pin broke but the gears looked pretty good just a little rounded on the corners