It depends, if you are feeding the 2802 with a £50-£150 DVD player and watching it on a 28"-32" TV with reasonable quality cables I would be suppressed if you could see any difference from switching via the 2802 or feeding the signals direct.
If however you are feeding the 2802 with a £500-£1000 dvd player and watching it on a 100" screen via a reasonable quality projector, then you would probably see some degradation in signal quality when routed through the 2802.
The purer the signal path the less chance for degradation is the simple rule of thumb.
But I would simply play a few DVD's with your system set up in a "direct" mode and the same with signals routed via the 2802 and see if you can see any difference.
I was using my 3803 to switch a Denon 2200 & NTL/Tivo into a PLV-Z2 projector and could only see a very slight loss in pq on some DVD's but not all (quality of DVD) on a 100" screen when using the 3803 compared to feeding direct.
I have however now purchased a Zektor HSD4.2 (feeds 4 into 2)so I can switch between a DVD2200, NTL, Tivo & PS2 between my PLV-Z2 projector and LC30HV4E tv.
If you can't see the difference then thats all that maters (you maybe loosing some PQ, but if you can't see the loss who cares).