I've almost exclusively used whatbox and it's been one of the easiest experiences for a seedbox you can have.
I think the most important thing to start off with is that the support is both high quality and extremely timely. The agents who respond to support inquiries are either native English speakers, or extremely convincing, as there's never been a failure of communication between us, and whenever I have a technical question, they're more than happy to help.
The wiki is extensive, and allows for people who are unfamiliar with seedbox-related concepts to learn and be able to utilize their seedbox more effectively.
You have multiple interfaces to choose from, including Deluge and rTorrent, I personally use rTorrent.
They have servers available in the United States, the Netherlands and Singapore. I personally recommend the Netherlands, as the download speed from that server is still roughly 4mb.
Storage prices are competitive, and while the traffic is unmetered, it still allows you a very reasonable amount of upload once you go over it.
Through the two years I've used it, they've had two promotions that were too good for me to pass up, and one is still ongoing.
Overall, to start out, I would recommend getting the $15 legacy seedbox to get a feel to if you like the tracker, and switch over to the HDD plan if you decide it's worth moving forward with.