Word documents suddenly take several minutes to open after March 22 Office update

I have not noticed the problem with opening documents, but generally my documents are less than 1MB. I have noticed delays in the Q&A: Word forums.

You could try rolling back to 2602.

For large documents, use of Style-based formatting becomes very important. The Importance of Styles in Microsoft Word. Here is a link to four very similar documentsi n a zip folder. Two each in .doc and .docx format, one is formatted primarily using styles, the other using direct formatting. The performance differences are noticeable.