I actually get the All the Whey unflavored whey isolate. I'll never get the flavored stuff again. You can drink it totally plain, even in a glass of water, and it's not unpleasant (just sort of like skim milk really).
The aftertaste you're talking about is the artificial sweeteners.
But the best part about unflavored whey is you're not STUCK with 10 lbs. of one flavor, you can mix up your own flavors, particularly if you have a little flexibility with your carbs you can add frozen fruit, etc. You can always pick up cocoa powder, vanilla extract, etc., use that plus the low cal sweetener of your choice to do the traditional flavor.