The role of noble rot is a complex process. it attacks the skins of the grapes to get to the sugars held within the meat of the grape. It does this by breaking down the skins, digesting them if you will. A process that is mimicked to a certain extent by producers using enzymes that break down the skins during fermentation. The proponents of the use of noble rot in the production of Amarone claim history on their side and posit that the action of the rot on the skins produces opulent wines rich in glycerine. A chemical that provides for a velvety mouthfeel.  
Opponents of noble rot wonder why they shouldn't start their production process with the cleanest grapes possible, even if they concede that a little noble rot might be helpful in producing a certain style of Amarone, They remain adamant that there is no way to control the spread of botrytis on the grapes. The proponents of the style suggest that an infection rate of about 40% is ideal for the production of Amarone. Simply put there are too many uncontrollable factors for many of the producer to feel comfortable with botrytis,  not withstanding the effects it can have on the actual flavors of the wines. It is an issue that will not be going away soon, though it seems that fewer producers are comfortable with Botrytis today than has historically been the case, with Masi being the largest and most vocal proponent. 
After Botrytis the biggest issue being discussed in Valpolicella is the role of the each variety in the blend, and more specifically whether Amarone should be a blended wine and if so if there remains a role for Molinara.  Traditionally Amarone has been a blend of Corvina and/or its larger berried clone Corvinone. Additional varieties such as Rondinella, Molinara, and occasionally obscure varieties such as Oseleta are added, either because of tradition, which can be hard to ignore both from a qualitative standpoint, as well as a viticultural standpoint, or to achieve a particular style. Briefly by viticultural standpoint I am simply referring to the fact that some vintners have the adjunctive varieties planted in the vineyards and may not have the means to replace them, or the vineyards to properly support Corvina or Corvinone.  
Today’s Amarone is increasing becoming a wine dominated by either Corvina and or Corvinone, with a bit of Rondinella added. Molinara is not seen as a noble grape by some and its use in Amarone is decreasing. To understand why one needs to understand what each variety contributes to the blended wine, and where Amarone is headed today. 
Corvina and its larger berried sibling Corvinone both offer a fantastic blend of relatively high sugar, good acidity and extract levels, and rich fruit flavors that, when grown in the right spots, are accented by rather profound spice notes and floral accents. The spice notes in particular are, for me, what sets apart a great Valpolicella, grown on south facing hills most likely, from an ordinary one. In Amarone some of the nuance is lost through the drying process but enough remains to add the needed aromatic complexity to make Amarone profound at times.
Rondinella is better suited to be planted on alluvial fans that spread across the lower reaches of gentle hills as they ease into the valley floor. Lower in acid and sugars than Corvina, Rondinella contributes richness, color, and extract to Amarone. Aromatically Rondinella is similar to Corvinone though more fruit driven and offering less of the spicy, floral nuance. 
And finally there is Molinara, a thin skinned, pale variety that at first glance might be mistaken for Pinot Gris. Molinari's historic role in the region was two fold. Most importantly it was and remains a prolific producer. Secondly its pale wine retains acidity and freshness, even when dried for the production of Amarone. Neither role seems to be important today. Producers are looking for power in their Amorone, not delicacy and climate change has shifted harvest dates, sometimes resulting in fruit that has more acid than grapes harvested at a similar ripeness level, though later in the year, in previous vintages.