This is perhaps the most misleading mod in this game. It claims to make maps easier and lumps a huge score penalty on the player for using it, and yet it does precisely the opposite: makes a great number of maps absolutely Insane.
There are a number of reasons for this:
1) The approach rate. This is the biggest reason. Most players, even new players, find faster approach rate easier than slower approach rate (to a certain point around 6-7 or so). Cutting the approach rate in half on harder maps is a HUGE change. Most Hard/Insane maps become completely unreadable because there are SO MANY circles on the screen at once.
2) Increased circle size. This usually makes it easier, but in a lot of situations it causes really confusing overlapping. Coupled with (1), the map is even more difficult to read.
3) Decreased overall difficulty. Yes, really. In osu!, you can't hit a note until the previous note either been hit or missed. By "missed", I mean that too much time has passed that you are no longer in the hit window to get a 50 on the note. A massive decrease in overall difficulty on harder maps makes the hit window for a note overlap with the "exact timing" of the next note in many cases. What this means is that if you misclick a note, yet hit the next one perfectly, you often miss it too because the previous note is still "active" and the note you clicked just "shakes", even though you hit it perfectly. You end up missing an entire chain of notes because of one misclick.
4) 3 life system. This doesn't actually make it harder, but it isn't implemented very well. It's incredibly difficult to resume playing after starting on the next life. Why? There's a completely unrhythmic amount of time spent waiting for the life bar to fill up again; it's impossible to tell exactly when you're supposed to start playing again. I think there's a button to skip this, but I have no idea what it is. The only reason I think this is because sometimes it immediately starts playing again without a wait. I've tried just about every logical button to intentionally skip it, and I've never managed to trigger it. Usually if I "fail" a map with Easy the first time (which is common thanks to (1) (2) and (3), I just immediately fail another 2 times.
5) Changes Insane maps far more than Easy maps. The Easy mod divides all the difficulty statistics by 2. This means that on an Insane (with AR/Drain/OD 8+), it makes a huge change. On easier maps (which it's probably intended for), it barely changes it at all. OD 1 ==> OD Half? Might as well not do anything at all.
So why am I bothering to post this? The "Easy" mod is misleading to new players! It makes things more difficult!
Basically, my feature request is to do one or more of the following:
1) Remove Easy mod completely.
2) Rework Easy mod to actually make things easier. How about letting the player choose their approach rate when Easy is enabled? How about dividing all the difficulty settings by 1.4 instead of 2.0 so it isn't such a massive change, or maybe just subtracting a static number? Reworking the "3 life system" so that the song backs up a couple sections so the player can get back "into the beat" when they resume?
3) Make the current Easy mode a difficulty increasing mod with a score multiplier (lol). It would certainly be harder than Hard Rock, Hidden, and even Flashlight on a lot of maps.
4) Something else?!
Ok sure, it would break existing replays on Easy mod. Thing is, there aren't many to begin with because it just isn't worth using to make a map harder, only to give less points. Most of the time people just use it to pass TAG4 maps with the extra life system.