People differ. I do think the button often replaces a comment. Before AMASS!, the best images in some popular forums, notably G&N, Wildlife, and Birds, attracted strings of minimally informative "Awesome shot" posts, like the tail on a kite. (This may also have happened in forums that I didn't look at. I wouldn't know about them.) "Awesome shot" still appears, but the kite's tail is shorter. Instead, the best images in certain forums draw great numbers of Likes. Why certain forums? Well, it seems to be a matter of local custom. Many great images are posted in Macro, too, but I don't see massive Likefests there.
In the Bird Portrait thread, it isn't unusual for a post to get 20 or more Likes. I don't remember any post getting 20 comments before Likes were available. A truly exceptional image might get 40 or 50 Likes, revealing an advantage of the button. If an image already has, say, 15 comments before you come along, you'll be less inclined to add a comment. At least I believe so. But if it has 15 Likes, nothing discourages you from giving it one more. So the button allows a distinction between images that are much liked and images that are much loved.
+1 




