Gamers do have the right and should complain about everything they possibly find wrong with something. There's a thing called customer feedback for a reason.
Also, GFWL is a pretty terrible experience for everything I've played with the service. First would be Dawn of War 2. The game itself loaded pretty quickly, then I had to sign into the overlay which proceeded to bog my machine down to shit. After a very long load, the game finally let me start playing. I wanted to play online with friends so I had to go through this, there was no "skip it and just play single player here" I had to go through this when online play shouldn't be a hassle at all. I mean, we've had good online play since Battle.net (and maybe before!), why should we stand for long log-ins and a completely pointless service. Sure, this is complaining about load times but that's important. Really damn important, I could say. If I were to time the length it would take to go through the entire GFWL process, I would say at least five minutes. Let's say I were to play a few casual matchs of SSF4AE, another GFWL game I played, about 30 minutes of play time I suppose. Five minutes of thirty minutes would be spent getting into the god damn game. And then my friend suffered massive disconnect issues with GFWL. He would disconnect randomly from the service, he never had issues with any other sort of netplay.
To say we shouldn't complain is utter bullshit. That's pretty much saying "accept oppression and take all the bullshit given to you."