I think the problem with page 42 is that 4e made improvised-action damage generally worse than just using an at-will power. I think that was a big mistake. The improvising player should almost always be rewarded. I was tempted to make the improvised actions 1/round minor actions.
If that was true, I'd agree.
But it ain't. I've got it open right now - thanks for the page ref, I'd forgotten!
So basically there are two damage tables - "Normal" and "Limited". Generally anything remotely clever or one-off goes on the "Limited" table (this is explained). That's doing much, much more than at-will damage. Stuff you could do over and over, which isn't really anything clever, just not covered by the rules, goes on the Normal table.
Then you pick Low, Medium or High, and the example given specifically calls out that you should try and make it do at least as much damage as normal. So if you're picking medium or low damage and doing less than a normal attack, well, that's on you as a DM for bothering to read the rules. You can also inflict status effects (the example includes a shove and a prone, as well as Normal-High damage). On top of that, depending on the effect, you could do AOE damage or the like, when you didn't have an AOE attack on your "menu".
The problem was the other one we've been discussing

That DMs vary. Some DMs understand the rules and are a fan of the players, and will use the Limited and High stuff generously, and inflict plenty of status effects and so on. Others will be stingy as hell because they don't get that this is stuff is literally explained in such a way that it should be as good as or better than normal powers.
Eek, one of my players is a moderately famous published author and has just started GMing for her writers' circle, I should be worried...
Maybe!