I'm sure every eng. student has asked or heard about this question...but exactly how tough is eng. physics?

Lets' say my GPA turns out be a 6-7.
Will I manage?

I'm thinking of nano systems/photonics.

I can't comment on the gpa part, but if you are interested in eng phys make sure you are very comfortable with math and physics..try to understand and do well in math and physics (both 1d03 and 1e03).

That's the first time I see a department posting such a warning:

"Due to the particular emphasis throughout the programme on the link between science and engineering it is highly advisable that students interested in Engineering Physics have a strong standing in Physics and Mathematics."
http://engphys.mcmaster.ca/undergraduate/admissions.htm

So yea, make sure you really like math and physics!

It isn't hard to get in, staying in is the hard part.

It's actually quite simple (not the course work... The answer to your question) : If you want to graduate Engineering Physics, you can graduate from Engineering Physics...

If you just simply want to graduate from a program, but your heart isn't in Engineering Physics, then you won't graduate Engineering Physics. Eng Phys probably has the best screening process: It cuts out those without a true passion for it... It KNOWS YOUR SOUL.... And sometimes it does a good job tearing your soul apart to get the truth out of it.

That being said, Good Luck!