I've seen this subject discussed on every H-D site on the internet- some feel that the 96 needs to run high rpm, others feel that it's happiest at low rpm. Six of one, half dozen of another IMO. :s
I haven't had any problems with lugging. The 96 is an undersquare engine (smaller bore, longer stroke) which is a design that generally favors low-rpm use and makes better torque on the bottom end of the rpm scale than an oversquare (large bore, short stroke) engine. This is evident in the modest 5500 rpm redline our v-twins have as compared to the 14,000+ rpm of an oversquare ricer engine. This is also why H-D recommends the shift point for 6th gear at 55 mph.
I noticed that a lot of the folks (on other sites) that were proponents of high-rpm-only-in-6th-gear suddenly found themselves loving life in 6th gear at 55-60 mph after IDS. :yahoo
IDS didn't do anything to reduce the "lugging" they thought they had, it simply dampened the felt impact of the power pulses transferred to the driveline by the engine at low rpm.
My 5th gear whines like supercharger on a top-fuel dragster :49: but I don't feel actual engine lugging till it gets below 50 in 6th...