I'm bugged like hell about the aliasing, too. It prevents being able to do high pitched notes from samples, being single cycle chipstuff to other recorded. It aliases badly, cubic and sinc make very little difference to my ears. Only upping the samplerate to something high (i.e. 96khz) makes a difference.
I guess the results there of "cubic" and "precise" - precise means sinc interpolation. I find it funny that most pulse responses (there are none for renoise tho) look like a pretty sinc pulse with preringing when samplers with little aliasing are shown. IDK whether applying such filters or methods would work out for realtime sampler action, preringing means added latency the better the filter the longer, and variable sample playback rates (modulated pitch) means such filter would have to adapt their curoff constantly resulting in mad computations.
Don't forget that probably many of the "good results" present audio tracks, or static resampling libs, or whatever, and not samplers with freely variable pitch? Trotzdem it'd be good to have tracker/sampler playback without aliasing, i.e. prefiltering or whatever. Will chop cpu, but I think it has to be possible?
Are there actual "samplers" with pitch modulation with real alias clean results and low cpu usage? I think there have to be methods to achieve this. Renoise makes o.k. tracker style sound, but has no option for real clean stuff - it's a pity. And it won't even provide methods for at least prefiltering stuff with autospread over the octaves, this can reduce aliasing as long as no hefty pitch modulations are used.