Agreed with Connie and Pendraia; for product creation it's pretty much the way to go. Distribution? Not so much.

Distribution is a different animal, and for content creators, the psd approach is extremely limited, particularly when it comes to something like brows, where people tend to want a variety of options. If you're talking about 'to prepare the product', vintorix, it's one thing; if you mean what the end user is delivered, it's another entirely. As a content creator you must be prepared to deal with the difficulties and eventualities inherent to both.

Pre-compositing all potential options on something like 'multiple brow types' isn't feasible beyond 1-4 color/style choices really at the most, which is less than what many end users want out of a product that promises versatility in this regard. (I've done blender/shader-based brows, transmap brows on brow geometry, and composited images with brow variations personally in charsets over the years; I have specific experience with all of the above to know precisely what I'm talking about on this one. ;) )

If you have supporting maps for bump/displacement/etc., it adds further to the file requirements. That's where shader-based approaches, or brow geometry with transmaps or grown hairs for mixing up the possible color choices and face map styles become valuable assets. They can be used in place of otherwise almost entirely redundant maps that also bloat an end user's runtime.

-D
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It's all fun and games until someone loses an eye texture.