I always like to check my gerbers before sending them off for manufacture. The best program I've found for this is Gerbv which, while it doesn't seem to be currently supported, still works well.
However, I'm finding with most designs recently I end up getting an error along the lines of 'Too many parameters to aperture macro'. Also sometimes pads, especially rounded ones, seem to render badly wrongly.
Has anyone else experienced this and found a fix, or can anyone recommend an alternative to Gerbv which works as well? PCBs made from these designs seem to be OK but it makes it harder to check them first.