Are you letting the unit fully boot before starting to use the unit?
The unit will always be slower than a Duo. The HD800SE CPU is single core 333mhz as per the VU+ Solo, Duo is dual core 405mhz.
Try zapping through bouquets, press down, select channel and press ok.
Through numbers I believe theres been a longer delay set accross the whole of the range of ViX images, pressing Ok directly after entering numbers will zap straight away.