So, I waited a few weeks before writing a review about seedit4me in order to have a better feedback and global overview of speed and reliability in the relatively long run.
It's been now 6 weeks and I can say that I am very satisfied.
I started out with their basic Sidekick plan and after 3 weeks, my 1 TB was almost full so I asked through support to extend to 3TB. The process only took a few minutes. So support is quick and efficient.
As for reliability, no issues at all. And concerning speed, the advertised 1Gbps are there.
Concerning usability, the interface is really great, clean and well thought out compared to other providers. Also there's a very nice selection of software you can install.
Overall, very recommended seedbox !