I think it's just a matter of generalizing vs talking about specific markets....
Yes, there's been fare reductions in the east - mostly where lower cost competition exists - and US is still the high cost provider of the industry so everyone else is lower cost competition. But saying that's there's been reductions in some markets doesn't mean that there'll no passenger will pay more post-merger than pre-merger.
On the revenue side, the US/HP merger "filled the gaps" in each others route map. Doug's favorite example was DFW, where neither airline could conveniently transport a passenger to both the east and west coast pre-merger but could post-merger. The merger made US a viable alternative for that type of passenger. Likewise, there were large portions of the west that pre-merger US didn't serve and large portions of the east that pre-merger HP didn't serve. We became a viable choice for passengers in those markets thanks to the merger. Thus the revenue synergy - we could sell tickets to folks that wouldn't have given either of us a second thought before.
Contrast that to a US/DL merger. Where can the post-merger airline take a passenger that one of the pre-merger carriers couldn't, especially DL? Very few places. Thus the revenue synergy can only come from one place - reduced competition, which allows raising averagefares in markets that would become relatively non-competitive. So some of the people that would have paid $129 for their flight might have to pay $159 or whatever because there weren't as many of the $129 seats available. US could legimitely argue that they didn't raise fares - the various fare levels might still be the same. But some people would pay higher fares post-merger than they would have without the merger with US and DL competing for their business.
Jim