I don't think this should be nerfed. Special room effects are rather uncommon, so it's good that some of them have very significant effects.

Furthermore, Pe is not so important, it's not like gaining 5 Pe is so powerful that anyone will grind for carrot rooms in the ID on purpose, I think...

It is perhaps just a little overpowered. But I think nerfing it more than a little is overkill.

So how about this? Potential maximum cannot be increased by more than 3 by one of those rooms, but the stat itself can increase by as much as 5. That way, it's more effective while your Pe is well below potential max.

The mere possibility of reaching 99 in every stat isn't a bad thing; it's when it comes at a low risk and comparatively low effort that it unbalances the game. Looking for carrot rooms in the ID is unspeakably tedious - not any less tedious than grinding for just about any other item, including the stat potions. Granted, carrot rooms can be found simply regenerating I:1 over and over, with near-zero risk, and I'm actually positive people have done it before; but I think they wasted an appropriate amount of time and effort doing it.

I think it's safe to keep this particular room effect unchanged. Keep in mind that there are no perception stat potions. There are no hard caps on any of those - and I always felt carrot rooms filled a similar purpose.

My experience is that your PE only goes up if your PE is below (or equal?) 30 or so.
I had a game where I found multiple carrot rooms. They stopped being effective, even with blessed potions, at some point.

Side note:
Carrot's don't really improve your vision - it was a cover story for the invention of Radar by the allies in WWII. It seems the lie lives on in German culture today, ha ha ha!

Oh, come on, this is crazy. Carrot juice rooms aren't even that common if you don't crawl or stairhop the Infinite Dungeon to find some.

What's next, deleting the ID because you can get Le and Ch to 99 like this too?

@Mobius drinking carrot juice at any old time increases Pe only up to like 19. But drinking in a carrot room (which are rare) gives you +5 each all the way to 99.

Also frog quest and all stat potions.

Can people please stop responding to requests with ridiculous over reactions? It's enough to say you don't support the idea. If things carry on like this we'll be hitting Nazi comparisons soon, and we all know where that leads...

From my perspective carrot rooms aren't a problem as is, and it's a cool little Easter egg effect in the game.

Like all good lies, it is partly true: http://en.wikipedia.org/wiki/Carrots#Nutrition
Beta carotene, metabolized into vitamin A, is good for eyesight, although it's safe to say that the effect is negligible in normal quantities.

Funnily enough, that same wikipedia article mentions that eating carrots raw is not very effective for getting beta carotene; a potion of carrot juice allows much more of the nutrient to be extracted during digestion. :)

I have made a minimal adjustment but actually don't see a problem... I mean: How many of these rooms do you truly tend to find?

Usually 0-1. And sometimes it's before seeing first carrot juice and often I simply forget that it existed or don't bother backtracking for it.

One per game, roundabout. I don't think there is a problem to see.

In my wizard stairhopping days, I usually found 4-5 in ID alone, while collecting spellbooks. I often left the location with 35-40 Pe, which mostly helps with view range but is not otherwise OP.
Potions don't need to be blessed. In fact even cursed potions of carrot juice work for this and there is no limit for how high can you increase the stat.
Other than ID, it's mostly 0-1 such rooms per game.
Since stairhopping is going to be much less effective in the coming versions, I don't think this needs any balancing at all.

I haven't gone to the ID for a long time, after some forum threads showed me the merits of descending through the UD... so I would say 1d2-1 per game too :) Even when I did spend more time there, carrot rooms weren't exactly dime-a-dozen.