The SAB has no notes on chapter 5, but I think there are a few things here that deserve comment. First of all, I've always thought it interesting that Moses' initial demand is not that Pharaoh set the people free, but only to let them go for a few days to freely practice their religion outside of Egypt. At least, that's what it sounds like when I read it. If this is indeed true, then I wonder if Moses is lying to Pharaoh, or if perhaps the intention was just to ask for a little bit at first rather than come right out and ask for it all. If Pharaoh had said yes, would they have come back after three days?
Pharaoh has nothing of it, though, whatever it is that they're asking. Instead, he decides to enact some cruelty on the Israelites by saying essentially, "If you slaves have time enough to waste my day with ridiculous demands, you're clearly not working hard enough," and he gives them more work. This is actually another place where I wonder if we're only getting part of the story, as Pharaoh claims of Moses, "ye make them rest from their burdens." Is he talking about the three or six days off they'd get if he gives in to Moses' demands, or is he making something up, or is there something going on behind the scenes where the people stopped working that day, and they're standing around waiting to hear what response Moses gets? I suppose that the scene later in the chapter in which "the officers of the children of Israel came and cried unto Pharaoh" points to them not really knowing what's going on, and therefore, it's not the latter. Still, it could be a matter of a few Israelites hanging around Moses; he had at least Aaron with him, and it seems reasonable speculation that they might have had a small entourage.
Anyway, the people get angry with Moses, and instead of accepting him as their savior, they accuse him of making their lives worse, which after all, he did. And Moses asks God essentially the same question that so many skeptics ask: Why does all of this have to be done the hard way? And in Chapter 6, God gives the only answer we ever really get, like it or not.