We record our services each week. We don't have multi-track recording on our system, so it's not the best quality, but it's good enough to hear what's going on. So I occasionally (by occasionally I mean 1 or 2 weeks out of the month) spend some time on Monday morning listening back to our choir, band, and myself as we led the congregation in worship. I'm listening for things like pitch, tempo, band "togetherness", entrances and cut-offs, etc. I'm always amazed at the things I hear on the recording that weren't evident to me during the actual service. I'm not sure that I've ever listened back and not heard at least 5 things that could be better.
Put yourself in the shoes of the congregation and listen back to what's being played on Sunday mornings. Don't have a way to record your services? Invest in one. Heck, you could even start with a tape recorder on stage if that's what it takes. Find a way to evaluate what you're doing. I'm always surprised at how I think I'm holding the tempo, only to find out Monday morning I got excited during the crescendo and sped up. Other times I notice my piano playing is too busy and needs to back off some. It doesn't matter if your congregation doesn't consist of all music teachers. I'm convinced that the more we do to fine-tune our songs, the easier it is for our congregations to enter in to worship.