The ergonomics on Delica 4 are not perfect. Firstly because the handle size is too small for sturdier hold. If you clench it tightly in your hand, the Spyder hole will pop out, although the back of the blade is optimized for thumb pressure. A bulkier handle could have made a difference without disturbing the dimensions.
Secondly, the handle of Delica 4 is 4.25 inches, which is too long for a typical pocketknife. The general length of a pocketknife is around 3.5 inches to be considered as a full-sized pocketknife.
Moreover, although the Spyder hole is bigger for smoother deployment, the steel liners inside the handle come in the way of holding the knife when it is open and cutting with it. Therefore, you may have to wear hand protection gear when using it. At the same time, it is missing a finger choil. Other Spyderco models have the finger choil, and Delica 4 could use it as well.
It also does not have a sharpening choil. Although that is fine, but Spyderco users may expect to see one, as do most Spyderco Delica 4 reviews.
It has a back lock, which is robust, but can be frustrating because they are not as straightforwardly closable as a liner lock knife by Spyderco. It closes just fine, but opening it requires placing your index finger at the corner of the opening, which has a sharp protruding edge. It can take some getting used to, even though it follows a simple technique. Moreover, a back lock is not free dropping in opening and closing mechanism, and requires a bit of wrist to twist it open. It is not a bad thing though, considering it can stay open sturdily and not close in on you in the middle of a cutting task.
The pocket clip is also painted and more delicate. It may easily get scratches and break, requiring you to replace it with a compatible and studier Spyderco pocket clip.