Text will not wrap after Import from Excel

Go back to your original XLS import file, for the activities with long descriptions, go into that particular cell, find the point where you want the line to wrap and press ALT+ENTER

You could even build a formula that does a replace for any description over a certain length such as:

=LEFT(B2,50)&"

"&MID(B2,51,250)

Where 50 is the length you want to wrap at, and press ALT+ENTER to create the linebreak.

Then reimport to overwrite the existing Activity Descriptions, and use Zoltan's method to increase row heights.

here is a trick ot get it to work

go to view table front and row

now uncheck Keep Current Row Heights

Check Optimize Height by row content and under that select Do not exceed and use 2 lines per row select APPLY and nothing happens 

NOW under that click on Select height for all rows and select 22 and then click APPLY

now Check Optimize Height by row content and under that select Do not exceed and use 2 lines per row

next select APPLY then select OK

this is a little work around that you can use

In your Excel import file, if you force a line break in a description cell, this should import into P6.

Be warned though, it wil screw up any exports to xls, or reports to csv output.