I have a DIR-825, but this is a general question about DHCP reservation.  I have about 20 devices on my network.  When I look at the device list under "network settings," the "hostname" for the computers are listed as their computer names, but I have a bunch of other devices listed as "unknown."  These are my TV, Blu-ray player, etc.  I can reserve an IP address in the DHCP section for each of them and type in the proper name.  That way, I can see all my devices listed by a real name (not "unknown").  This allows me to identify any rogue devices that might sneak onto the network since they would be in the dynamically assigned section.  
Questions:
Is it problematic to do DHCP reserving as a general practice?
When I reserve the DHCP address for a device, will the router automatically assign the new reserved IP address when it sees that particular macid coming online?  I don't have to set anything on the device itself, right (except for the device to receive an IP address automatically, which is usually the default)?
I have a printer that I have currently assigned a Static IP address (inside the printer).  I can put this address outside the DHCP range or I can put it inside the DHCP range but reserve the address.  Is there any difference or preference?
My configuration is:
Cable modem -> DIR-825 router -> dlink 24-port gigabit switch
then off the 24-port switch are:
DAP-1353 wireless access point extender
5-port dlink gigabit switch
I reserved an IP address for the 1353.  I also gave it a separate ssid.  Anything special I need to do with the 2 switches?  Ok, I'm really showing my ignorance now.
Thanks!