One thing that's been puzzling me is about the frame, and various opinions I've seen. Mainly that it's not worth upgrading beyond low end components. I understand that the sum of the parts can be more expensive than the whole bike, but assuming you avoid the LBS prices and labor charges, what is the issue specifically?

The frame weighs four pounds. The lightest frame you can get is two pounds. Generally speaking at rational expenditures, we're looking at a pound to a pound and a half heavier than a carbon frame. So if you used the components of an 18 pound CF bike you'd have a 19 to 20 pound "Denali". Is that a deal-breaker from the frame alone?

No doubt there are differences in handling characteristics. Stiffness, road vibration, "feel" whatever that is, and so on. I wouldn't know - probably most owners of such low end bikes have little or no time in the saddle on high end bikes. So I'd like to hear from those of you who have spent time on both. What are the serious, deal-breaker drawbacks of the frame itself other than the extra pound or so?