Hi everyone,
As most of you are in the same situation as I was/am, I am writing this to clear some doubts on this subject.
I have done the GMAT online on the first day it was available, so I will describe a bit of what was my experience in order to help those of you who are still deciding wether to wait or to do the online exam.
As many deadlines for applications are coming to an end, I decided to take the risk and do the Online Exam. Please be aware that the link for the exam will only be available half an hour before the scheduled time. I had no idea of that and was panicking 45min before the exam thinking that I did the application wrong. And I would advise you to contact the GMAT Chat more than half and hour earlier, as the waiting times are really high during this period.
After the link was available, the procedures were really fast and I was ready to start the exam.
About the exam itself, it was exactly the same as we have available in Practice Exams:
1. Quantitative: Not easier, and the White board is not the best - sometimes it would erase everything written and can be distracting. I haven't used anything other than letters and numbers, as I was not used to the circles and the other available options. (I did one of the Practice Exams using Word as my whiteboard)
2. Verbal: Exactly the same.
3. IR: Exactly the same (with the same disadvantages of Quantitative)
Overall I had some technical issues with whiteboard and a pop up notification from my computer's memory that didn't close the entire exam. The proctor can be distracting as well, as sometimes, if you ask for help, he pops up and asks if everything is ok 5mins later when you no longer want the help.
A week later, I haven't received the grade yet. However centers are still closed in my country, so I will still be getting the grade earlier than if I had waited.
In my opinion, I would do the GMAT Online and if something goes wrong, you can always do it again when centers open.
Feel free to ask any other questions concerning the exam

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Update:
My grade was definitely not what I was expecting, 80 points below my average usual grade. However don't be discourage by this, my Quant scores were high, meaning the whiteboard was no problem after all. I got a really low Verbal Score, blame it on me and not on the Online Exam

Best of luck to all of you