I went the CR-1 route back in 2004 and Visited DC montly! BUT it boils down to is the port of entry (POE) officer!! 1 should always have proof of ties to Canada in ur possesion! But keep in mind you have no "right" to be able to visit the USA. So even with 100% evidence ur going to return, they may still deny you entry----all comes down to the POE officer. Many of us visited and had no problems, but some do get questioned more, some get taken into secondary for more questions and some do get denied! Like I said, I had no problem, never once was I asked for evidence (which I had on me) Great FREE forum is visajourney.com has all the info u need! Even a cr-1 forum, step by step instructions, etc etc. my 2 cents:
Canadians Visiting the USA while undergoing the visa process, my free advice:
1) Always tell the TRUTH. never lie to the POE officer
2) Be confident in ur replies
3) keep ur response short and to the point, don't tell ur life story!!
4) look the POE officer in the eye when speaking to them. They are looking for people lieing and have been trained to find them!
5) Pack light! No job resumes with you
6) Bring ties to Canada (letter from employer when ur expected back at work, lease, etc etc)
7) Always be polite, being rude isn't going to get ya anywhere, and could make things worse!!

Have a plan in case u do get denied (be polite) It wont harm ur visa application if ur denied,that is if ur polite and didn't lie! Refer to #1