Some of the responses here display the anti-science attitude which I find very frustrating in this forum. The vast majority of speaker manufacturers will measure the frequency response of their products, as well as a host of other parameters. An estimated in-room response (based on a large number of on and off axis frequency response measurements), such as that measured by Klippel, actually will do a pretty good job of indicating how the speaker will sound in an "average" room. It doesn't tell you everything, of course...distortion, directivity, impedance, sensitivity...all are important. I wouldn't buy any speakers based on data without listening, but I would certainly rule some out based on data.
Should Speaker Manufactures provide a Frequency Response Graph?
Eric at Tekton Designs has been battling two different reviewers who have posted measurements without his permission, using Klippel devices for their respective measurements.
It seems to me that if manufactures provide a simple smoothed out graph, consumers can see how much a speaker is editorializing with a frequency response that deviates from neutral.