My initial reaction was that this was a great idea, and a complete no-brainer... but I went ahead and engaged the old brain anyway, and found a concern or two.
With the high amount of traffic MacRumors gets, it would probably make a fair bit of scratch from the program.. enough, quite possibly, to make the affiliate program the primary source of revenue for the site. (not predicting that it would turn the site into a paying concern, just closer to break even)
Now, 6, 12, 18 months down the road, Apple decides that it has made a big enough impact and either A) discontinues the affliate program, or B) Dictates that sites affiliated cannot do rumors. Neither of those are in any way out of the scope of the kind of stuff Apple has pulled in the past. (Pulling press access for rumor sites, dropping popular programs leaving companies in the lurch)
So I think it bears consideration, certainly.. but I would be very reluctant to allow it to become too great a part of the revenue mix.
Just my thoughts.