Quote from sprstpd:
Here is the reason why it sucks for me. I do some of my trading in pre and post-market. It has always been the case that ARCA's uptick policy during extended hours has been irritating compared to INET's policy. In the example in the first post, the last print on ARCA on HAL was 83.65 and now there is an 83.64 bid on ARCA. If I send an order directly to ARCA or via IB's SMART router to short at 83.64, the order ends up showing as a limit sell order at 83.65 on ARCA. If I really wanted to get short, before I could send an order to short at 83.64 or lower to INET and it would be displayed on the INET limit book. I tended to have a good chance of getting filled when I matched or crossed the market on INET. However, now if I send a short order at 83.64 or lower to INET, the order is not displayed publicly. It is flagged as a hidden order and no one else knows it exists. So my chances of enticing someone to get me short on HAL are practically zero now.