I know that most of the stuff we need to plan for a flight is contained in the release. The release breaks down the planned fuel for each segment, usually fix by fix. I believe you can even find what winds and temps they used to calculate all the stuff and compare it to what the forecast is calling for. On top of that, it's even more of an advantage if one of the crew members has flown that particular route (ORD-JFK for example), because some legs are killers when the weather is crappy.
I've had a few days where dispatch just isn't using their "vision" to plan our flights. One night, at Skyway, we had to add some fuel and get an alternate because there were T-storms around Des Moines. Not enough to create an alternate from a legal stand-point, but enough weather to make a Beech crew nervous about where to go when in an area, low on gas and low on altitude (for radioing home). We knew we could go just about anywhere if we had to, but it's better if everybody's on the same page, ya know??
At CHQ, we had a flight to JFK that nearly got into an urgent fuel situation because we had very little play fuel and no alternate. There were storms around and by the time we were in the air everything was starting to slow and hold. At one point, the captain had one radio and I had the other and was flying, while he was trying to get a game plan set up with dispatch. We were being told, by ATC, an EFC time that was not going to work if things didn't really pick up at that point. For a few moments, no one could hear me on my radio and I was tapping the Cappy on his shoulder (for his radio) while making a very necessary turn around a cell that was literally on top of us. Fortunately, ATC came up and said they saw we were turning and would keep the space clear ahead and knew we were trying to talk to them. We got to JFK, but not without some big-time urging with ATC to keep us moving, me thinks.
All that being said, it doesn't make me nervous one bit to land with 44 minutes of fuel or a little less on a clear and million day after having had to be vectored around more than usual. After all, planned fuel burn is exactly that- planned fuel burn. When I get close to reserve fuel, I let ATC know exactly what I need to get to the airport safely. I'm honest and they can, in turn be honest with me and allow me to plan for whatever is necessary.