You can install any OS on your phone that is meant for 9530... Don't be afraid, it will work. Just delete the vendor file. I have installed all the leaked OS on my phone and I've never had any problem.
I have also upgraded mine (Bell Mobility) to 5.0.0.328, no problems. Phone transitions are quite smooth. It always amazes me how slow Bell is to roll out updates.... there was almost a class action lawsuit over the Samsung Instinct.
I am on Sasktel, a bell affiliate, and the only problem I've had (like some other people) is the lack of full blackberry browser (only WAP browser, so I'm using Opera 5 till the service books support this version). Other than that the new version works amazing and theres no way I could go back.