For me, an enquiring practitioner is a professional who is able to adapt the way they teach or learn based on critical research in to what works and what does not work. It is someone that is capable of reflecting upon their own previous teaching/learning and think critically about how they could better themselves. This evaluative process is intrinsic to being an enquiring practitioner.
The benefits of being an enquiring practitioner are that you are able to develop and improve the curriculum along with other teachers which would stop the curriculum from staying set and rigid and would mean it is constantly being modified to improve upon it therefore providing students with a better education over all. If this is the case for the curriculum then it enables general improvement of the educational institutions themselves and means that every school will not necessarily be teaching the same curriculum. It also provides teachers with a capacity for self-improvement in terms of the way they plan lessons and teach the curriculum. Being an enquiring practitioner would also mean that a teacher would be more likely to take constructive criticism and use it to refine their own lesson plans and style of teaching.
The challenges of being an enquiring practitioner I would imagine would be it would be difficult to align your way of thinking if you were not used to the process of enquiry and evaluation as it is difficult to challenge your own assumptions. Some would also argue that enquiry is fairly limited as it is contextual as even if one approach works in a school somewhere, it does not necessarily mean that the same way would work in a different place. The process of enquiry can also be rather slow as there is no real fixed end point as you can steadily continue to improve yourself for an indefinite period of time. Many classroom practioners who use enquiry can get off topic but the enquiry needs to be connected to teaching or learning.
I believe that if I want to be a successful teacher and continue to improve my teaching style and ability to educate that the process of enquiry and evaluation should be at the core of my planning and practice.