I gotta go with Pa(b)st Prime on this one.
I was in favor of stock decimalation at the time the debate was raging, although I personally thought they went a little over board. I would have liked to have seen 0.05 increments down to say $5 priced stocks then maybe penny ticks. I don't trade stocks any more but if memory serves I was thinking some ECN's support sub penny increments? To me that's just plain silly.
I was opposed to the NQ tick reduction, but I do still trade it.
I'm opposed to the ZB and ZN tick reductions. I like being able to take a tick, cover commissions AND make a profit.
If the ES tick size was 0.50 I could maybe see an argument for 0.25 ticks.
I don't normally use the DOM during RTH but I will look at it during the slower/thinner AH session. Seems to me a tick reduction in ES will render the DOM less useful and at 5 levels deep maybe even near useless.
It seems to me that smaller tick sizes in general make scalping less and less worthwhile.
I suppose at the end of the day the number of market participants, open interest and money on the side lines will remain the same. Smaller tick sizes will just spread it out over more and more price levels. In this case I personally don't see any significant advantage of that to us the retail trader.
If your not profitable with ES 0.25 ticks, 0.10 ticks is not going to improve your situation.