I'm fine with the railroad, but there are a few exceptions.
First, I like to be able to go off track on small things, and expect the railroad to fit with that. IN other words, I want to have the option of taking that pirate ship we fought on, converting it, and using it as our base of options, WITHOUT this necessarily having been something the GM planned on. I want my PC to be able to befriend journalists or bartenders on the fly, and be able to use those contacts later on.
In short, I want to be able to act like I'm not in a railroad, and not get hit with "well, you can't do that because it would screw this up"
Second, if I'm in the railroad, I want to be important to its conclusion. I once played a game where the three PCs (my spellthief, a cleric, and a monk) were around 4th level, and our PCs followed four NPCs of 6th level for a while. And watched as they kicked butt. And then got destroyed by ogres. When we tried to run, the Ogres caught us. So when we fought, they defeated us. Gah.
Third, if it's known I'm on a railroad, I don't want to be hit with "non status quo" adventures and then told "well, not everything in this campaign world is built for your party to handle". Actually, yes, yes they are. And you established that early on. It's unfair to hit us with something we can't handle and then use that excuse when we get beaten. And yes, I have done this to my players, and yes, I regret it.
Fourth, I want the cool scenes to be even cooler. In a loose game where the GM reacts to the players, my "awesome cool stories" will consist of my player cleverly using the environment to best some orcs or gnolls or something. In a heavily railroaded game, that is not enough - I want stuff blowing up like mad... because you've planned for this stuff. It needs to be dramatic.
Finally, I don't want to follow a railroad simply because I'm required to. I HATE games where I make a character in front of the GM ("yeah, a tribal ranger sounds good to me...") and then get hit with large portions where I'm useless ("a tribal ranger sucks in this campaign, it's a city campaign..."). Or, to use an actual example that I've already touched on, I don't want to make a spellthief and then find out a few sessions later that magic is apparently really rare in this campaign.