There's a post on Critical Hits about the horrors of boxed text. I will state quite bluntly, here and now, that I hate boxed text. Some of my reasons are the same as in that article. In general, it's just too stilted, and honestly, I don't believe that that a GM should deliver descriptions as if reading from a fantasy novel.
So what do I prefer to boxed text? Keywords or phrases. The GM should craft a description that fits the players, and fits what has recently happened or what has been established about the characters. If there's the absolute need for a sentence or two, for example to describe a sequence of events triggered by a trap, then that's fine, but then it should be written in what the article calls "third person", although really it's an objective impersonal voice.