I am using "DZ Auto Harvest" http://oblivion.nexusmods.com/mods/17984 which works like a charm and does exactly what it is described to do. It doesn't conflict, it doesn't steal, and it auto harvests everything.
My only problem with it is: it auto-harvests EVERYTHING seemingly in the entire cell. It would seem that that sometimes means harvesting all flora that is within a couple hundred feet of the player character.
For example, if you enter Market District and turn DZ Auto Harvest to "active" mode, you will hear this *ZzzzAaapp* and every flora item in the entire Market District gets checked for harvest. You might fail on a significant fraction of them so it is not like EVERY item within 'range' is automatically put into your inventory, but every item in range is checked for harvesting.
I have always liked the alchemy part of the game a lot. Learning where flora are located and spending the time to walk around to them is fun a lot of the time. But, I find that with the vanilla harvesting mechanics the target areas for the flora are so small that no matter how much I enjoy alchemy and the harvesting part of the game, the constant minute adjustments in player position and cursor location, combined with having to switch View modes constantly, eventually just gets too tiresome.
So, on the one hand vanilla harvesting involves the tedium of having to make minute adjustments to get your cursor in JUST the right position to harvest a flora item; DZ relieves that tedium but goes too far by effectively making that "cursor area" the entire CELL!
What I would really like to find is a mod that offers more of an "intermediate" harvesting mechanism somewhere in between that of vanilla harvesting and that represented in DZ Auto Harvest.
Say for example, instead of having to get the cursor just right, if you point your cursor in the direction of a clump of Bergamot and get within a fairly short range, then click USE it would harvest everything that was within a five or ten foot radius of the cursor.