Sources of protein
I actually prefer Whey Protein. On the contrary: if Queal was using plant-sourced protein, I wouldn't have settled with Queal in the first place. You said it yourself: Whey is one of the overall best quality one can get. As a weightlifter, I care about getting quality protein.
My only gripe would be that getting 100% of your daily proteins from Whey is, to the extent of my knowledge, sub-optimal. A mix of Casein and Whey, as found in cheese, is reputedly superior.
However, since I use Queal only for lunch, and still have regular meals otherwise (and me being French: with plenty of cheese), I don't mind it being only Whey.
Sources of carbohydrates
No opinion -- I would have to try a low GI version to be able to compare. I lift 6 times a week at lunch and run 3 times a week in the evening, but I always do it fasted, before eating, so the current short term energy release doesn't really benefit my workouts. Perhaps a lower GI might net a small energy gain, but I honestly doubt it.
Strongness of flavours
Heh, it's a tricky question, and I think it depends on what you like. For flavours I love (Chocolate, Chocolate Hazelnut, and RIP Chocolate Peanut), I wouldn't mind a stronger flavour. For flavours I only "like" (Vanilla, Strawberry), I would prefer a milder flavour. And for flavours I don't like (all the others), I wouldn't care.
I would much prefer more options. As you might recall, I've had a completely bland Bacon batch, which left me unsatisfied. To quote myself: