Recs.
Updated
SpecsUpdate
Pros
Pro SVG Support
In the era of "retina" displays, 4k UHD, 5k, and even 8k, Scalar Vector Graphics - independent vector images that can scale to any resolution without any display quality loss - are more important now than ever.
And this tool is quite capable of rendering true SVG output suitable for consumption at any display resolution (not a big bunch of rasterized bits in the document, actual paths, points, etc.).
Pro Integrates well with Affinity Photo
These are companion apps & switching between them is built in - Photo is a very powerful raster tool with a feature set close/better to Photoshop, it will also use some Photoshop plugins. This allows you to add-on powerful raster capabilities if you want them - but doesn't force you to.
Pro Sketch Alternative (Great for Mixed OS Teams)
For those working in mixed environments that aren't 100% MacOS, you'll find devoting yourself to Sketch.app brings with it...pain. If this fits the bill for what you need feature-wise and you're in a mixed OS environment, it's a very capable replacement for Sketch.app. Note that it doesn't have all the same features, but then again it doesn't need all the same features. Short of organization differences inside the document you're working on, there shouldn't be anything you can't do with Affinity Designer that you could have with Sketch.
Cons
Con No Preview for Export Function
When exporting graphics for the web there is no chance to get a preview. The only thing you can do is export multiple formats and compressions and compare the results afterwards. People have been asking for this basic feature for four years now, but the developers have different priorities. -- This would be a nice enhancement.
Con Treats all objects as filled
You can't select objects on the canvas by clicking on them, if they're surrounded by another object (like a rectangle or a frame). Designer treats all objects as filled, so if you've drawn a frame or outline or an object with a hole in it, you can't select objects within that hole directly. You have to laboriously iterate through all objects in a list until you get to the one you want. This is an extremely common situation, which cripples the entire product. Very surprising and unfortunate defect.