Answer:
I would add a comma after "feature" to separate the independent clause that follows it. Here's the revised sentence with the added comma:
"Despite all of this, there is still one redeeming feature: ebooks weigh less and take up less space than physical books."
The comma helps to clarify the sentence structure and make it easier to read. It indicates a brief pause and helps the reader to distinguish between the introductory clause and the main clause. Additionally, the colon after "feature" indicates that what follows it is an explanation or clarification of the feature mentioned before.