halemano:
I would be interested in your source for the no diving for 24 hours after landing rule, could you please tell who's rule that is?
Unless you are a 100' freedive photog or spearo with monster wave tow surfing proficiency and you find a great instructor willing to spend 10-12 hours with you each day, a 2 day crash OW course will not give you much more than Scuba Diver skills and even with the above requirements met, I would question the professionalism of any instructor/shop that would even consider it.
I meant to write SHOULD not.... I usually avoid diving the same day I fly, but MAY consider it the next. I do usually sit out a day - if nothing else, my body could use some acclimating to the time zone, weather, etc.
By mentioning that you COULD get the course in 2 days, again, it would depend on getting all the books/KRs done in advance of showing up at the door. To say you cannot do it is a bit presumptious in my opinion. I was able to complete my OW cert in 3 days without doing any reading beforehand. That did impede on my vacation though since it was pretty much read all night and morning, do reviews mid-morning and C-W and O-W sessions in the afternoon. Shops will work with you and if you need more time to develop certain skills, then just ask the instructor.
Just because you get OW certified (from any agency) does not mean you are ready to hit the ground running without professional assistance, but it would allow you to feel comfortable at open-water depths without feeling the need to rely on professional assistance.
Each person is unique in how they handle minor issues. Some people will take 50+ dives to feel comfortable with buoyancy, issue resolution, etc. Others may be there much sooner or much longer. Since the initial poster asked for opinions, I threw mine out.
As for the questioning of professionalism, PADI standards call for the process to be handled in certain ways, but the only limiting factors are time, the correct procedure, the ability of the student and the instructor and the fact that no more than 3 training dives can be completed in a day. It truly is possible to get the OW class done in 2 days IF you do some pre-work.