I am used to dressing somewhat casual for church. I typically wear jeans, a nice collared shirt, dress shoes, and a blazer if it is a little cold outside. I hardly ever wear a tie but when I do, it is in addition to the afforementioned manner of dress.
We sometimes visit reformed congregations when out traveling about and there are times when my wife and I find ourselves underdressed although we are not looked down upon. In one particular church, all of the men were wearing suits and ties although it was quite obvious that for some, it was not something they were used to. One guy had his tie all messed up and halfway out of his collar and you would think he would have seen it in a mirror and corrected it or (quite obviously) his wife would've done so! My wife is all over me about stuff like this which keeps me from looking like a clown out in public!