I have same issue
My new iPad AT&T 4G signal is 1 bar where I got 3 with my iPad 2. And it isn't just an indicator issue. The actual speeds are slow and sometimes it completely stops. I've disable LTE but no improvement.
I may visit my local AppleStore but I'm sure the signal there is probably 5 bars. This is frustrating because I absolutely love my new iPad except for this.