What concerns me is how fast they've come up with it. I trust vaccines that have been well established and thoroughly tested.
It has gone through as much testing as any other vaccines. The reason it has been quicker is because the administrative side of things was sped up, not the actual testing. It usually takes months or years to recruit enough volunteers - these trials managed that in a matter of days. Usually trial proposals, ethical reviews, operational guidelines, etc. sit in some committee's to-do list for months before getting reviewed, before being passed to another committee and waiting several more months, and so on. You can wait months or years for the FDA to get round to looking at it. All this was skipped and these trials went straight to the top of the pile.