I was content with the $20 option to use my existing iPhone plan (6 GB). I didn't think it was a great deal, since I assumed it was $20/mth, but fair enough. $20/mth makes sense in relation to the other two items since I will be offloading my iPhone use onto it, and it keeps me locked into Rogers with my iPhone at the same time.
Now, things are different! Even if Telus/Bell are the same as Rogers with cost, I will switch to them out of anger, with the iPhone to follow. I know Bellus is no better, but it will still feel good.
Yes, the iPad plans are cheaper than the normal going rate, but remember, they are cheaper because Apple has locked out the ability to tether with your phone - Rogers needs to add that $20 option back, pronto.