I guess you could look on trackitt, or you could do a straw pole on here, CIC do say it does not make a difference, especially if you are applying from a non visa country and you have a simple life ie no kids, no interesting background!!
The main reason they send back, is if you do not fill everything in!!!, however even lawyers can have a bad day, one case, a lawyer friend got client stuff sent back as he filled in a Stat Dec in BLUE ink not BLACK!
If you have a complex family history, are from a country which is not English, French speaking I would recommend a lawyer, if not clear the dining room table, brew a big mug of coffee and get down to it (with a black pen of course ;D )