It is really developer friendly. It's designed for resellers and people who host their client's websites (as well as being great for just individuals). The support is really good - they are responsive and very helpful (no silly questions!). The servers themselves run really well and have good uptime stats. They fix issues timely. And it's a nice interface that's easy to use.
I like that 20i offers both email hosting and domain services in the same control panel, which is convenient. I appreciate how clean the interface is, making it easy to navigate. It's also easy to talk to support, which I find helpful. Additionally, the initial setup was very easy.
I had an issue with transferring a domain to 20i. They were **VERY** responsive and helped me work out the problem even though the issue was with the original host. Their pricing is reasonable.