it scales back slightly the decentralized and fee-less nature of Bitcoin, which are important features to many of its supporters.
This is a dumb complaint. Even if you think Bitcoin is great, there's no way it's going to do away with financial middlemen and transaction fees. Those things exist for too many different reasons. And even the fees it will eventually do away with, there would have to be some intermediate state between now and then, where businesses rely on some other business to deal with the processing of Bitcoin transactions, since Bitcoin hasn't become accepted as real currency yet.
Oh yes, I know, I'm going to get a whole speech about how Bitcoin is just as real as the US dollar because fiat currency is all made up and imaginary and all prices are set by the market and bla bla bla. I'm not claiming that Bitcoin isn't worth anything, but just that it hasn't been accepted as currency yet. If I can pay my bills or buy something with Bitcoin, it's the exception and not the rule. Plus, the value of Bitcoin is still very volatile. In practical terms, buying Bitcoins is more comparable to a speculative stock investment than it is to converting money into another currency.
So the reality of what's happening is, due to some level or customer demand, or maybe because they got a no-lose deal from their bitcoin processor, or perhaps it's just a publicity stunt, Dell has decided to accept a volatile stock as payment. Whatever you pay in Bitcoin immediately gets turned into dollars-- so Dell is really still working with dollars, but they've allowed a bitcoin payment processor to work as an intermediary to convert to the transaction into dollars.
It's a neat development, but you can't expect Dell to operate on Bitcoins at this point.