I like how easy it was for me, my team of 3 people (2 developers & 1 designer), put together this application using only HTML/CSS! The fact you don't need backend services or programming language knowledge makes things even better since there are so many options available now-a days when building applications online such us ours - which requires no coding at all but just drag drop functionality etc.-it really helps save time by not having someone else do those tasks instead doing them yourself! We also used Bootstrap CSS framework too because its free open source software where everything from design layout code structure has been made already done especially if your looking into creating mobile apps then bootstraps css files will come handy here :).
As mentioned above i think one downside would probably being more expensive than other platforms maybe? But overall great experience working through these two companies they were very helpful during development process :).