I updated my debriefing in the Share Your Experience sub-forum, but since people seem to be asking questions in this thread, I thought I'd chime in with some observations.
So I took the test on Wednesday the 22nd but got my scores today - so less than 7 days total!
I got a 790 50Q 51V....I don't think my score is very relevant since I am a full-time tutor and know the exam inside and out, but hopefully some of my observations can be helpful to others.
Some have commented that the Verbal section felt very hard and that many questions didn't seem to have a clear right answer, but I really did not find that to be the case. It felt very straightforward and not that hard. And I don't just mean subjectively, I mean objectively speaking (or as objectively as I can be). I am constantly reviewing people's practice tests (official ones on mba.com) and seeing Verbal sections in their entirety and the Verbal section of the online test felt very, very manageable by comparison. I guess I hesitate to say easier, but it did feel easier to me. And not having a physical whiteboard seemed to be a non-factor for me.
For Quant, I obviously still did very well, but I certainly felt pretty handicapped on some questions on the Quant section. As
VeritasPrepHailey indicated, there were definitely Quant questions that necessitated writing things down, sometimes a lot, so I struggled on those and guessed completely on one that I judged too difficult to do without a physical whiteboard. But as I wrote previously, the section felt balanced with some very hard questions and some not that hard at all.
Personally, I was just totally unprepared for how I would use the whiteboard. I didn't even realize that it could be resized and literally had to move it out of the way on every question as I tried to click next and then confirm the answer. And although I spent about 5 minutes playing with MPrep's sample whiteboard to see which tools I would use, I just didn't do any practice questions with the whiteboard to even see how or when it could be used most effectively.
I am also not someone who would be comfortable typing anything Math related, so I was trying to use my finger and track pad, but I think for people who are more comfortable typing (and typing Math in particular), there probably would be a way to be more effective with the online whiteboard. There is just no getting around the fact that you are still at a disadvantage without a physical whiteboard, but I think if you were to practice a lot with it and have a good understanding of when and how to use it, you could minimize the disadvantage.
I haven't 100% confirmed the following, but if my understanding is correct that the score essentially lives on a separate score report and can essentially be buried, and if it's also true that you don't even need to wait 16 days to be able to take the in-person GMAT and that the online GMAT doesn't count towards your 5 times per year limit, I don't think there is much downside in doing it - it's almost like you get a free shot at the GMAT (free minus $200, lol). It's like taking a pretty expensive, albeit pretty realistic practice test (realistic in the sense of the anxiety and fatigue and other intangibles that are in play when taking the actual GMAT).
Hope some of this helps you intrepid, would-be Online GMAT test takers out there!