with it being an IPO, i usually wait til after the lock-up period to see how many of the initial investers stick around and if the stock stays stable.
while i love and miss Tim Horton's donuts, i think @ 28.17 is a very steep entry point. until THI starts marketing like it can be a direct competor to Starbucks, i wouldn't feel comfortable buying in @ more than $18/share.
Disclaimer: These are just my oninions and should not be used as investments tips
(and yes, i know Starbucks is not a donut shop, but i think THI will expand more to follow the success of Starbucks)