Excellent Responsive Support
I recently started using Quickprosp. So far so good, but the reason I'm writing this review is the top notch support.
I've reported a couple of issues over the past weeks. Each time support answered and reproduced it, then told me what was actually going on rather than sending me back to my own settings. One turned out to be a bug in their code and they said so plainly. Two others they confirmed and queued for a deploy, and they were clear about which was live and which wasn't yet.
The deliverability one impressed me more than it probably should have. I sent raw email headers with my own reading of them. They re-ran the checks themselves and came back with where I was right and where my test had a hole in it.
Worth saying, since support quality so important and it's almost impossible to judge support before you buy.