I don't like them at all. Yes, they look pretty, but it's an emulation of the worst aspects of paper forms. The grid-style form is my least-favourite paper form and I frequently find it confusing and difficult to fill out such forms correctly. Perhaps this is because the linear flow of the form is awkwardly two-dimensional, or perhaps because for anything beyond a trivial example, the layout becomes unnatural as the size of the fields don't usually lend themselves to a logical and human-friendly structured layout.

Perhaps it's because the grid style form ignores the importance of whitespace in clear and understandable design. Here's a good test: hold the form upside down and see if you can still tell it's structure at a glance, or hold it at the other side of the room and try the same thing.