For those wondering, here is our experience with Covid testing on the island today:

We have an afternoon flight on Saturday, and opted to test directly at SLS laboratory (St. Maarten Laboratory Services in Little Bay) this morning, to stay within 72 hours of departure. (American Airlines customer service was unable to tell me if we would be allowed on their flight if testing on Wednesday morning at our resort - technically within 3 days, but more than 72 hours, so we decided to play it safe and go to the lab on Thursday.)

Registered online - easy to do with the instructions on their website. Very responsive to emails. Set up our patient portal passwords to get results.
Arrived at 8am for an 8-8:30 am appointment window. Sounds like they do ALL appointments early morning. There were approximately 40 people milling around outside the entrance when we arrived, all masked.
Lady working for SLS handed us a number for our group, we were #27, and they had just called in #11 from the 7:30 am group. Groups ranged from 1-8 people.
We had to wait outside until called to do our final registration and payment before testing - we were called in for paperwork at 10:10. Took awhile to do the paperwork, even though we had provided all the info in an email prior and set up our passwords on their patient portal prior to arrival at the clinic.
After completing the paperwork we were directed to a shaded tent in the back of the clinic - from there we were called almost immediately for testing, which took just a few minutes, and were back on the road at 10:30 am. Total time elapsed was 2.5 hours, we did not expect to wait so long with an appointment!
Received our results in the patient portal this evening, sometime between 4pm and 9:30 pm.

Takeaways:

1)Even though we had an appointment, it took almost 2.5 hours before we were actually tested. I felt bad for people waiting with kids and babies in tow! You have to wait outside, and there was very limited shaded area to stand in. They did have 5-6 chairs on the sidewalk, and steps to sit on, but most had to stand. I suspect part of this was due to it being the start of ramped up testing and working out the kinks.

2) Traffic from Oyster Pond to the lab in Little Bay on Hamster Ave was slow! Took us about 35 minutes to get there, we left at 7:25 am.

3) The people working at the lab were SUPER nice, and everything was very clean and professional feeling. Very diligent about everyone wearing masks, sanitizing hands, etc.

4) We had our results back the same evening, which was great.

5) Cost was $75, we paid cash but I did see some people using credit cards.

6) A guy I was chatting with as we waited said one of his friends was denied boarding back to the US yesterday as his test was more than 72 hours old (it was 77 hours old), not sure if that was on St. Maarten or elsewhere, but that was what he told me.

Hope this answers some questions for those wondering!