Over the years I've seen many types of team. Some teams believe that they have to cram as much in to a sprint as possible and work up to the 11th hour to get it all done. I used to think that way too. This can lead to, amongst other issues, the team working too all hours on the last day of the sprint. This is especially true if there have been unforeseen issues.
If you're able to do that successfully each sprint then more power to you, but I prefer a slightly different approach.
Though the term sprint suggests that we should hurry though as many stories as possible (while meeting the definition of done), I view the sprint as agreeing to a set of stories and creating them the best way you can. i.e. making them awesome (I know that sounds a little cheesy but couldn't think of a better word).
The approach I prefer is to build a little slack into the sprint. This means that the final day can be used slightly differently.
A little slack gives the team some time for innovation and learning, plus allows preparations for the sprint review. It also gives a little break from the constant slog.
Some people may consider this waste as it's time that could be used to potentially work on more valuable stories, but I look at it as making the product and the team more awesome.
What do you think?