Most "classic" tobasco I've had lately just tastes like vinegar and black pepper - no discernible heat. Of course, that may be because so many restaurants store their jars of tobasco for months on end and all the volatile organics degrade - the ingredient list includes cayenne, which I normally find pleasantly warm AND flavorful; but I've not been able to detect that flavor in most jars of classic tobasco.
The jalapeno version is better flavored, although also completely lacking in heat. I can feel a little warmth in the chipotle flavor.
I've not really had a pepper that clocked in much higher than 1,000,000 SHU, and when I've gone that high it's not been a whole fresh pepper (I've enjoyed plenty of dishes that contained a 1/4-1/2 teaspoon of powdered Bhut Jolokia) so I don't have a point of reference for the absolute top of the scale.