I've also heard it is easier to obtain a better DA trigger with the SA notch removed.
Lighter, maybe, but not automatically "better". Smooth is better than light. Grant Cunningham, a respected revolver 'smith wrote about this a little while ago, and I included links below. Good reading.
As far as the merit of DAO, you'd obviously lose some of the versatility of a revolver, but if you don't think you'd ever use SA mode, there's a real case for rendering a gun DAO. Cunningham wrote about that as well (see link 3). He mostly discusses it in the context of a SD gun, but as far as tuning, he does mention that the DA pull on a DAO gun can be lightened lighter than the same DA/SA gun, since such a tuning DA/SA gun would "result in an unconscionably light SA pull - often below 32 ounces."
My own view is that the real benefits of a DAO aren't primarily via a lightened trigger pull. IMO, the primary benefit is increased accuracy through a faster lock time and less hammer jar. Given the same trigger pull (i.e. spring tension), a lighter hammer will travel faster, reducing the "lock time", which is the time between when the sear broke and the hammer hits the primer. The shorter the lock time, the less time you have to move the gun around during the lag. Also, it's the hammer's kinetic energy that ignites the primer, but it's momentum that jars the sight picture upon hammer strike. Since kinetic energy is proportional to the
square of hammer speed, whereas momentum isn't, you can lighten the trigger pull somewhat to achieve both a faster lock time and less hammer strike. Pretty cool. I posted
this before, but it's an example of a very light hammer strike with a very light hammer. I didn't have any accurizing done to the gun when I had it tuned, but I immediately noticed an improvement in accuracy. It's a real tack driver, and that video shows part of the reason why.
But...lightening the pull too much can open a can of worms you may not be prepared for, so before you go off and decide you must have a super light action, you need to know about the "cons": A super light action may lack enough hammer energy to ignite all primers reliably. Federal primers are known to be the softest, and those with very light pulls must reload using Federal primers only (and have you ever tried finding them in the last 1-2 years?), and even then, they often have to hand-seat the primers fully in the pocket. A real PITA if you ask me.
A super light action may also expose a bad habit many revolver shooters have: riding the trigger. The pull weight is a result of the tension in the mainspring and return spring. A properly-tuned gun has these tensions relatively balanced, so to seriously lighten the pull, the return gets seriously lightened as well. If you're in the habit of riding the trigger (i.e. letting the trigger push your finger to the start position), you may very well find yourself short-stroking the trigger. Short stroking happens when you pull the trigger before it fully resets - between the 1st "click" on the return (resetting of the hand on the cylinder) and the last (resetting of the DA sear). The result is that the cylinder rotates, without the hammer rising and falling - the gun fails to go boom. Believe me, it's a serious drag when it repeatedly happens in a match while the timer's running.
Finally, for all but a select few, a very light action isn't really necessary anyway. I've also shoot my bone-stock 3" Model 64 with fixed sights in IDPA and have done just as well as with my 686. Most people get it in their head that a light action will enable them to pull the trigger faster. And it may. But here's the thing...IDPA, ICORE, USPSA, etc isn't about how fast you can pull the trigger - it's about how fast you can see and how efficiently you move. A light action will actually impede your progress if you get in the easy habit of pulling the trigger faster than you can see the sight picture.
Finally, one more thing: Any discussion & advantages of DAO mostly assume a bobbed hammer, which those J&G guns, for some reason, don't seem to have. Bobbing the hammer is pretty easy, though. I have a friend with average mechanical aptitude who did his own with a dremel (after removing it from the gun, that it) and it looks and function great.
http://www.grantcunningham.com/good_trigger.html
http://www.grantcunningham.com/blog_files/action_performance.html
http://grantcunningham.com/blog_files/the_case_for_dao.html