1) Disney will interfere in Marvel's creative process.

2) Disney will exploit Marvel's stable of characters.

3) Marvel will get "dumbed down" to appeal to a younger audience.

To the first point, I believe there is a long history of Disney being "hands off" creatively in the profitable companies they acquire, especially those that appeal to an older audience.  Miramax, for example, is a Disney company.  They have released such gems as Pulp Fiction, Kill Bill, volumes 1 and 2, Dogma, Gangs of New York, There Will Be Blood, No Country For Old Men, and Swingers. I have never heard a complaint alleged that Disney interfered with any of these films.  I cannot think of any Marvel characters, even under the MAX Comics imprint, that can compete with the grittiness of some of the above mentioned films.  It is logical, form a business perspective, to assume this same philosophy would extend to Marvel .

The second point is clearly being made by people who don't go out very often.  You can already find Marvel characters gracing everything from toothpaste, to pacifiers, to cake mixes (yes, really).  It is hard to think of a way that Disney could exploit merchandising rights any more that what Marvel has already done on their own.

Finally, the idea that marvel will somehow get "dumbed down" to appeal to Disney's core audience of "tween" females.  Disney already excels in this market.  They don't need Marvel to sell more products to 12 year old girls.  They are trying to break into new markets with the purchase, so any fundamental changes would undermine their intended purpose. Not to mention that Marvel has been trying, unsuccessfully, to break into the younger markets with the Marvel Age imprint for some time now.  They may actually have the money and marketing ability to tap into that market now.

And that is, at it's core, why this announcement should be good news to everyone who likes either company. Marvel will have more money to take some risks and really flex it's creative muscle and Disney will have a new reservoir of creative talent to tap into and revitalize some of it's sagging brands.  The only argument I really can't defend against is the concern that too may companies are merging which could lessen diversity.  Unfortunately, that is a topic for another discussion.