Support isn't the best. I was attempting to restore a very large database and they shut down my instance for using excessive disk and CPU. I didn't get any response of what sort of limits to stick under.
Otherwise they are very similar to DO but with more data centres. The only complaint otherwise is their instances start a little slower. The API is very easy to use though.
I had both Vultr and RAMNode servers, but shut them both down and moved them to DigitalOcean.
The control panels in Vultr seem like 3rd party reseller ones akin to the cPanel/WHM days. I was not able to upgrade my Vultr VPS to a larger one with a few clicks like I expected to be able to (and am able to on DO and Linode). I guess you are expected to put in a support ticket or something. It felt very much like a basic Xen setup, though they have made recent strides to help with that.
With DigitalOcean, I can upgrade my VPS with a few clicks, and even downgrade them as well if the storage disk is not expanded when you upgrade. I am very impressed with their offerings, and the ease of use of their control panel setup.
I maintain VPS across different providers (Linode, DO, vultr, budgetvm, etc) and haven't had any real issues with them. Based on my interactions with their customer support, the level of support you receive is about what you'd should reasonably expect from providers in that price category.
The only real gripe that I have is that they don't statically route the /64 they assign to your VPS so I have to run a ndp proxy daemon.
I colocated with a sister company of theirs for a year and a half and I found them to be very reliable. Vultr provides free DDoS protection in their piscataway ___location but if you do not require that I don't see a reason to use them.