I dunno... this is not like software with a single, simple purpose and once you have a v1.0 it's just bug fixing and adding some features. An emulator is always a work in progress and even though the 4.0 release was considered 'stable' back then it was actually a lot less stable then recent build. There may be a little regression for a hand full of games, but pretty much everything is better in recent builds: they're more accurate yet also faster, have more features, the code is cleaner, almost all sources of crashes have been eradicated, etc...
Intel i5-4690k (Devil's Canyon) @ 3.5 GHz (+Scythe Mugen) / Gainward GTX 1070 Phoenix (OC'd) / ASUS Z97 PRO GAMER / 16GB G.Skill DDR3-2400 CL10 TridentX / X-Fi XtremeMusic / Win10 Pro 64bit / Dell S2716DG Monitor / 3x original WiiMote+MotionPlus+Nunchuk