You can start a new sketch from scratch -- and obviously need to in the beginning. But Forge also lets you start from an existing sketch, prompting you to copy desired layers from it.
As of now, the only control you have over the brush is its size. Opacity can only be changed on a layer level, and while it's easy to get thicker, denser strokes with most of the brushes, if you need a light stroke you need to use the pencil or airbrush.
The brush toolbar displays a preview of the current brush at the current size setting. It changes in real time as you change the brush size and color. The supplied brushes are pencil, ink, paint, marker, airbrush and an eraser.
In project view you can rearrange the various Ideas to rank and compare them. Here, I've got the references on the right -- layouts and the images I pulled palettes from -- and the color tests on the left.
If you want to hide Ideas, you drag them to a pile in one of the corners. As with a real pile, you then have to either pull down each sketch sequentially to find the one you want to retrieve, or pull them all out and individual return the ones you don't want. I think that's taking skeuomorphism a little too far.
While it doesn't yet support any palette creation tools like Adobe Color, you can still manually create palettes using the colors in an image. When you drag the circle off the color ramp into the image it turns into an eyedropper.
This view shows you all the projects you've created with thumbnails of the sketches (Ideas) within. The free version of the app supports only two projects.
Importing from drawings created with Adobe Shape can be useful, since the app doesn't have any predefined geometry tools (e.g., lines, squares, circles). To change layer opacity you slide sideways across the layer thumbnail.
When you left swipe on a row of swatches, it gives you the option to duplicate or delete the palette. To create a new palette you have to duplicate an existing one and edit it. Adobe Color support is on Adonit's radar.
Currently, Forge can only export as PDF (and that only to Dropbox or send via Message or Mail) or PNG.
You can directly import from or export to Dropbox, which is nice if you're a Dropbox user. Creative Cloud and Google Drive would be welcome, too.
You have a few options to set as shortcuts for the stylus. Using one for undo is a lot easier than the two-finger left swipe.
One thing I don't anticipate changing is Forge exclusively supporting Jot's styluses for pressure-sensitive sketching. You can use passive styluses, and Wacom's pressure-sensitive models work with it, albeit incompletely. For example, you can't program the buttons on a third-party stylus.