I often feel that the places that 4e falls down are often a result of false starts. The game may have the core of a good idea, but fail to pursue it far enough. One of the best examples of this is tempo - the pace of encounters.
Historically, D&D has had a problem with the "5 minute work day", where players would load for bear and go into an encounter guns blazing, using all their big spells for a quick, decisive win. They would then withdraw and rest long enough to recover spells and repeat the process. Numerous GMing techniques have emerged over time to try to mitigate this behavior, and players have responded with more and more clever tricks. It's simply such an effective technique that it will always have some allure.
4e took steps to reduce this by changing the power structure so there were fewer buffs (spells that enhanced a character over a period of time) and fewer one-shot abilities. Characters would always have their at-will powers and usually have their encounter powers, and that left only the daily abilities. This meant that there was no longer the problem of the "useless" magic user being left without options, and that was a big help, but there's still some temptation to go whole hog with the dailies, then recover.
To offset this, 4e introduced a pair of tempo mechanics. First, you'd pick up one action point every 2 encounters, and if you took a long rest, your pool would reset back to 1 AP. Second, some of your magic items would get better after a certain number of encounters. The idea behind these mechanics was straightforward: to provide incentives to keep pushing on rather than just stop and replenish resources. It was a good idea, but fell short in practice. The magic item improvements were fiddly and rarely worth the effort, and the action point economy was...flawed. Setting aside spending limits and slow accumulation, there was a simple piece of math that if you used you AP in your first encounter, there were two ways to get it back: have another encounter or take a long rest. The optimal choice was pretty obvious.
But the thing is, I like the _idea_ of tempo a lot. I really want to give players a reason to conserve their dailies and push on without feeling like they're being screwed.
One obvious fix is to change up the action point economy. Give more points, allow broader use of them and so on. This is an interesting enough topic in its own right, but I worry a little bit about it because decisions of use vs. stockpile always seem to work better on paper than they do in play. It tends to go to extremes of behavior very quickly.
So I'm now considering something much more simple: grant a tempo bonus equal to the number of encounters so far. That bonus applies to attacks and damage but not to defense. So after encounter #3, you're at +3 to hit and +3 to damage.
Now, my first instinct was to back off from that as overwhelming, maybe cut it down to +1 per two encounters even, but I think that's wrong. The bonus needs to be immediate and appealing enough to offset the loss of recovery, and by allowing it to escalate dramatically, you introduce some real choice. After the 5th encounter, you're hell on wheels, but you are probably also very nearly dead on your feet. Do you take a break and give up that huge bonus, or do you push on and risk it? Remember, your defenses aren't going up, so even though you can kill enemies more quickly and reliably, you're still going to be taking hits.
To me, that feels like a more substantial choice. One with real opportunity costs, and one that invites more complex spending behavior than is currently encouraged. What's more, once I get past that reflexive twitch against giving the players an 'abusable' option like this, I think about the things it invites (less whiffing, faster fights but with real risk) and the possibility that it moves the "sweet spot" a few encounters deeper into the dungeon, and I really like it. A lot. Enough that I wish I was running it right this second.