Rabbi Ari Enkin over at Hirhurrim has a very educational post regarding the practice of wearing a hat and jacket during davening. His fairly comprehensive halachic survey of the topic is very on target, and is definitely worth reading.
My own practice during the week seems to conform with the position Rabbi Enkin explains regarding how davening attire should conform to the way a person (as an individual, though not as a community) would dress when making a public appearance, which for me would include a blazer/jacket.
Rabbi Enkin also makes an interesting observation that never crossed my mind before: wearing a tie during davening. Certainly, the standard protocol for "dressing up" these days would include a jacket and tie (but not a hat), but no halachic persona seems to indicate the need to do so. That's definitely a very sharp point that can be used against the nit-picky people who say a hat is necessary, evn when it is no longer part of the standard formal outfit.
However, the post does not mention the particular practice of wearing a hat only on Shabbos/Yom Tov, which I addressed in one of my earlier posts. This isn't to say that Rabbi Enken missed this practice, since it seems to be part of a hashkafic, rather than halachic, notion at any rate.