No one (serious) thinks that Mozilla cannot deliver impressing feats of engineering, at the very least because they've got quite a bit of tail left on their goo

No one (serious) thinks that Mozilla cannot deliver impressing feats of engineering, at the very least because they've got quite a bit of tail left on their goodwill for breaking the IE monopoly. What people are implicating is their strategy. As others have mentioned, they don't seem to lead entry into any space, and therefore their presence in the space is constantly in the vein of catching up. Thus far, the only clear reason I've ever heard them mention is the same "open web standards" argument. Obviously this approach is valid, but with their browser success they should know better than anyone that you cannot overtake Goliath with open standards if no one is using your product. Lo and behold, they've apparently shown a product at MozCon that Google and Apple have already bet a ton on and released compelling consumer offerings for. Regardless of how impressive the APIs and UI may be, history repeating itself here.