I can't say for sure as I've not used the TalkTalk box, but I have the Humax. The remote is sometimes sluggish to respond (but is okay most of the time), and the TV guide usually takes 1 to 2 seconds to populate the programmes that are on now, so this could be just the way the boxes work. Best bet would probably go to a Richer Sounds / John Lewis and see if they'll set it up so you can try it out.
On the other hand, both Huawei and Humax are bringing out new boxes (link) so might be worth holding out for them, even if just means the older ones drop in price.