As long as you're competent you will do fine. I never got the impression that they were hard on me. From what I've been hearing, all the people who flunk out have extremely poor instrument skills. One of my instructors told me about a CFI-I with about 800 hrs who couldn't fly to a VOR, couldn't hold, couldn't fly a procedure turn and never got established on the final approach course on a nonprecision approach. Last I heard he was on about his 4th additional training session. They will work with you but eventually they have to cut you loose.
Most of my instructors seemed impressed that I have my CFI and actually instructed full time before coming there. Most of the new hires are fresh out of various certificate factories and can't fly instruments to save their life.
To make a long story short, as long as you are good on instruments you will do absolutely fine.
-MJ