Without understanding how the assessment is meant to be used or how it has been validated (doesn't sound as though it has been validated from the abstract), it's hard to make any sort of judgement about how useful it might be.
If it is just meant to be used as a cognitive aid to remember what factors to consider while planning for an intubation, it makes sense. Although for that purpose, I think a little more formal and comprehensive checklist is probably a better idea.
I don't think it's likely that a tool like this will ever be useful as an actual predictor of intubation difficulty. The specificity of the factors listed is not nearly great enough to build a reliable tool on. It's a safe bet that someone with a mouthful of vomit will be a challenging intubation (we don't need a formal assessment tool to tell us that), but someone who is very large or very small won't necessarily be. Poor neck mobility can make an intubation more difficult, but not necessarily.
When I'm doing a pre-op, I always ask the patient to demonstrate Mallampati and neck mobility, and as they do that I visually estimate inter-incisor distance (mouth opening) and thyromental distance. Things like a huge neck will be apparent too. If all those factors agree (either all favorable or all unfavorable) then you have a pretty reliable indication of whether the intubation will be technically easy or technically difficult. Quite often they don't all agree, of course, in which case you just sort of go by your overall impression. Like E tank said, it's really more of an eyeball test than a formal assessment.
I think of and approach physiologic factors separate from anatomic ones. Someone who is septic or has a really bad heart needs to be approached differently than someone who is perfectly healthy of course, but that really just comes down to your choice of pharmacology and has nothing to do with the technical difficulty of the intubation.
No matter what predictors you use, you will be surprised at times.
In the field where things are inherently more challenging, I think the most important assessment question to be answered is really "does this patient actually have to be intubated now?" If the answer is yes, then everything else becomes secondary and all you have to focus on is the basic steps to optimize your chances of success. If the answer is "no, probably not, but we're going to do it anyway" (which I think is the majority of prehospital intubations), that's when it becomes really important to have your ducks in a row and get as good a handle as possible on what you might be getting yourself into. In a true emergency, the priorities are clear and there's little blame to be placed if things don't go well because it was just a really challenging situation and you had no choice but to make an attempt. It's the "elective" ones where you really own it when you makes that choice and things don't go well. I think that's the assessment that we should be focusing more on in EMS airway management. I think for all the focus on airway management education in EMS, we don't see nearly enough emphasis on learning how to judge when to pull the trigger and when to hold off.
