I tried every free slider available in WordPress and none of them did what I needed. Finally I went with Smart Slider, and it's amazing. So many options, there's more customization than you can imagine.
But when I installed it, the sliders were not loading properly. I contacted support, and they went above and beyond. They logged into my WordPress, figured out the issue, and fixed it very quickly.
I am very impressed with this plugin, and the support they provide.