I'm not currently using any virtual walls. I've also tried using Pierogi near and far from the base station. I did read on the manual how the IR ports can be blocked by those devices. It's to bad because it would be nice to be able to remotely (via IR) start the iRobots cleaning cycle since the unit I have doesn't have the scheduling feature the higher models have.
I have a Samsung 7000 series LED TV. According to my tape measure, Pierogi works fine up to 10ft (~3m). Anything out of that and it is a hit or miss. Is that distance consistent with your tests?