The examples I've heard at the RMAF, incuding Roger Russell's array and the Audience arrays, sounded very good to me, but they did lack that last bit of "sparkle" you hear with a high quality tweeter.
And here is Russell's explanation of comb filtering in his line arrays, which concludes that it is clearly measurable but it isn't an objectionable quality. His conclusions are consistent with my brief listening experience, but I would need a more extended listening opportunity to be convinced.