Cakewalk has been oh-so-very-kind and included a VST wrapper (I\'ve forgotten who from now), so GPO & HALion (and any other VSTs or VSTis) work quite well.
As for the Tascam US-428, are you referring to using it as a control surface? I found it a bit more responsive in that regard; however, I use the US-428 as my audio/MIDI interface--it lives underneath my desk on top of a VCR. Therefore, I really can\'t comment in detail about that aspect of it.
P.S. FWIW, the Sonitus plugins are really, really nice with a very small performance footprint--i.e. they sound good without sucking up an undue amount of resources. The VSampler is...OK in my book, though I did use the included electric guitar almost immediately.