For testing when the supply of EU is irrelevant, the debug tool is great. It isn't however the most useful tool when it comes to more obscure things like crops and brewing, where documenting is still rather hard, as information is based off mostly random events for crops, and brewing it seems no one has looked at in any depth since 1.2.5 (not that I expect it to have changed either though :P). It'd be nice if the debug tool had information for what growth stage a crop was on, as well as what type it is, and potentially things like hydration and nutrient value of the soil and air quality, along with more information on booze barrels as they ferment, like the hops/reeds-wheat-water ratio, what it would currently produce, and how long until it changes to the next thing (if it can). Wiki wise having a way of telling a block's hardness/resistance would be nice too.
These wouldn't be all that useful if they piled on top of the current debug output, so I'd suggest another mode (switching with mode switch key and rightclick most likely) which would output the crop/brewing information, and a third one for the hardness/resistance of the right clicked block.