I'm surprised to say this, but they use Comic Sans MS perfectly! Most other tools run in to the danger of looking like the final design. If you give less sketch like mockups to devs they might copy them pixel perfect without thinkng a bit or your client might dislikes the ugly "design".
Sometimes you have to copy+paste a lot, but it's worth the simplicity (there is an option to reuse elements across pages, but it didn't seem worth the complexity, so sometimes I paste the new menu bar on every page again for the final design, takes 5 mins and is usually fine.)
Its fast enough to even use it for internal communication of implementation details for UI stuff. Often much easier than writing a lot.
Regarding web: you have to make 2 mockups and do one mobile version, one non-mobile version. Most web stuff is quite simple in structure though, so I often just do it in my head and dive straight to photoshop for the actual design and do the even simpler mobile version just in CSS.