Rick,
I think the latest and greatest flat tappet cam profiles have much more lift and fast-ramp action then their counterpart ancestors did in the 60s, 70s and 80s. Accompanying spring rates have increased proportionately too (therein lies most of the problem). That, combined with Chinese lifters and a poorer grade of iron in the cam cores, comes together to complete the nightmare. There's just too many negatives to sway me towards a flat tappet in any performance motor that I'll build. In fact, given the same engine, the hydraulic roller will develop as much or more HP than a solid flat tappet will, at a streetable rpm. Of course, as with all things, there'll be exceptions to the rule.
Flame-on Ernie!
Dave