Praia - your "light pop on the lead" is exactly the reason I really don't advocate using flat collars. You are jerking your dog's neck and many a McTimoney animal chiropractor will be able to tell you the number of dogs whose necks are put out by exactly this kind of thing. The subsequent tension that builds up in the neck has a ripple effect throughout the body and can (and does) cause behavioural problems.
The other issue with giving a "pop on the lead" is that people tend to do this when their dog is reacting to something, which can in turn make them more reactive (as they are usually reacting as they're worried about whatever it is, and that reactivity can be as mild as pulling on the lead, but you then give them a jerk to their neck which they may associate with the thing they were reacting to, and so you end up with their fear increasing).
As a Ttouch practitioner I always recommend to clients that they either switch to a harness, or they walk the dog in a balance leash (where you use a long lead which you hook around the dog's chest so you end up with two points of contact and the pressure is to the chest and not to the collar). I have worked with many dogs when they are being reactive to something, straining on the collar, up on the back legs barking at something, and the simple exercise of wrapping the lead around the front of the chest and holding them this way so that you take all pressure off the neck, can be enough to get the dog to really calm back down.
I generally do not advocate anti-pull harnesses as they physically stop the dog from pulling and I agree that some people rely on this rather than training the dog to walk in balance. However some dogs are REALLY pully and an anti-pull harness can be a starting point as you can then click and treat the dog the moment it's in balance, build from there and then switch to a normal harness.
Personally I think you can have far more control over a dog in a harness with two points of contact - it is much easier to guide a dog in the direction you want by leading from the front, firmly stroking the contact from the chest and looking in the direction you want to go so that the dog has very clear signals, both through the contact on the lead (stroking the lead encourages the dog to move whereas "popping" the lead just feels very unpleasant and sets up more tension in the body), and through you looking at where you want to go (as the dog will follow your eye direction).
I don't really understand your view that "you won't really know how well-trained your dog is until she's back on a flat buckle collar and lead" - if your dog is walking to heel in a normal (not an anti-pull) harness then she IS trained!
