The K&K is absolutely not lacking in the bass in any way, shape or form, in fact it is an extremely rich and natural-sounding pickup. Feedback is not an issue for me - I use mine either through my Roland AC-60 acoustic amp, or direct through the PA. Either way, some EQ-ing and judicious use of the notch filter removes any feedback issues that occasionally arise (and USTs feed back too, given the right circumstances - it's a fact of plugged-in life for an acoustic guitar).

The only thing to be careful of with the K&K is input impedance issues - the usual I/E of preamps such as the Baggs Para-DI is 10 Megohm, whereas the K&K requires 1 Megohm. If you have such a mis-match, the resulting sound can be thin and unsatisfactory (which may be where you got that impression from, Richard?). I use an Orchid active DI-box which has an input impedance of 1 Megohm, spot-on for the K&K, and I've never heard a better amplified acoustic sound.