Pros
No pros factors to be mentioned, as I have not started work with them. But be honest, I can't really offer a one-star rating for their behaviour and attitude shown for this case.
Kontras
Not sure what is happening with Tenable, being one of the bigger player in the Infosecurity market. You words and commitment needs to be fulfilled. When you mentioned that you will revert back with an concrete offer on last Thursday, and I waited till Saturday before decided to give up as I have emailed both your recruiter and hiring manager to enquire on the status of the contract offer, I did not even get a reply. In the Security industry, verbal commitment is equally important, hence I hope Tenable will reflect on this and change for the better. You should not convince the candidate to resign first, then await for your offer. What if you did not offer, just the same in my situation. Do not put people in a difficult situation, as you would not wish people to do the same to you. I have not even seen an apology email sent. Is that what Tenable really can offer?