Yeah i understand ! I had a reference letter and copy of contract (i don't know if that's required for EE as well ) one employer prepared those in 2 days ! the others , said "ok we are working on those" and i'm waiting for more than a month now ! completly ignoring my emails .. !
For OINP, I spent a few hours preparing reference letters for 4 different employers and then asking them to sign and prepare for me. One of them prepared the letter the same day! Two others took a week or less. The most important one took almost 2 weeks, but at least I got the letter after following up with a couple people. So now I have the reference letters for OINP and post ITA, but unfortunately I did not have the foresight to register for OINP immediately after getting the final reference letter, as it closed less than day after.
So I'm still waiting both for OINP to reopen and then for ITA.
I have heard that depending on your location, it can take some time to schedule a medical exam. CIC allows you to get your medical exam before ITA. See "Get your exam before you submit your application" under "When to get your exam":
http://www.cic.gc.ca/english/information/medical/medexams-perm.asp
However, some doctors might require you to have ITA first, so you would need to check with the individual doctor. I am planning to get medical exam as soon as I receive Ontario nomination, maybe even before.
Translation of foreign (not in English or French) documents can get delayed if you have any documents that need translation. The translation service I used for OINP told me it would take probably 24 hours but up to 48 hours. Instead, it took almost a week to receive my translation, and then I had to keep following up to receive the certified, notarized copy.
As others have mentioned, there can be significant delays in getting FBI PCC for the US, although if you are a US citizen or permanent resident, you can go through channelers with a 1 week turnaround time.