What's great
First of all, one of the few truly European cloud options you can choose from.
They offer quite a lot of different services, everything from bare metal servers, to databases, S3 storage, Generative AI.... you name it.
With this many options, similarly to other big cloud providers, the UI becomes a bit of a nightmare - although I personally think that they solve it a lot better than Azure or Google Cloud (AWS is somewhere in the middle imo).
It's pretty quick to spin up whatever you need, the pricing is fair and transparent and as a little extra they even show an estimated CO2 footprint based on your configuration.
What needs improvement
The UX all over the place. There's often banners, boxes, ... popping in a short time after load, which can get really confusing. Other than that I really don't have much negative to say since it's in my opinion much more of a pleasure to work with and use than aforementioned players.
vs Alternatives
I'm using Hetzner for other projects, but Scaleway just has a ton of features and products which are just not available over there.
GCP, AWS, Azure are all big platforms of organizations which sometimes make questionable use of their power and only loosely EU. Scaleway is a very welcome alternative to that.

Google Cloud Platform
Vercel
AWS
Hetzner
Azure