Since priority club is free to join(just like others) I would say it's definately worth the five minutes to sign up just in case you ever encounter another IHG property. Other than that, if your stay is going to be 5 days or more, you could get enough points for another free night stay for your own leisure. I don't think anyone can get away with discounts towards rooms in any matter but there is a list of extra you can get at Crowne Plaza's at their link here:

http://www.ichotelsgroup.com/h/d/cp/.../passpriv.html