Agree or disagree with the following statement.

"Measurements provide a fairly good indication of how something will sound..."
IMHO ,measurements,even good ones,are no indication that you will like the sound

Statement:

If you have never listened to any particular component, you can't have an opinion on how it sounds.

You are always entitled to an opinion, it just won't be an "informed" opinion. Just as someone may have an opinion of food that they have never tasted. Opinions carry different amout of weight, I usually give more weight to someone's opinion if they have actual experience. However, everyone is entitled to an opinion, on anything, regardless of how informed, or misinformed that opinion may be.

Remember the old line: Opinions are like a$$holes. Everyone's got one and they all stink! Jmcgrogan2 is right, you're entitled to your opinion and the weight that anyone places on it is up to them to determine. The more information used to form it, the more weight it may carry.

If opinions were limited to only what one has heard this whole forum would be about 1/4 the size it is today.

Then again, it is usually impossible to comment on a single component when heard in the context of an entirely unknown system, with speakers and cables and room and electronics that are new to you too.

But ... none of that stops anyone from venturing an opinion on anything.

At some point, measurements will be telling, but usually I thinks it's a mistake to judge a product solely on its specs. It's usually a good idea to listen before reaching a conclusion.

In fact, I'd go a step further and say that - Even if you HAVE heard a component, it's tough to definitively have an opinion of how it sounds. System matching and ESPECIALLY room matching are critical.

You can look at specs and rule out a component for use in a given application - a mini monitor that's down 10db at 100hz probably won't do well in a 5,000 cubic foot room, but that doesn't mean that it sounds bad. A really poorly designed product (horrible on-axis response and power response in a loudspeaker, for instance) is probably a decent indicator that a product won't sound good in any application, but IME such products are pretty rare.