It should work fine. Make sure that you've deleted older drivers first. You don't say how you are connecting the printer -- Ethernet is more reliable than USB or FireWire in my experience. I'm not sure what you mean by "doesn't seem to activate". Do you mean the proper driver doesn't show up in the "Print Using..." dropdown?
Make sure you have the most up-to-date drivers from Epson. For the 4800, it is file epson12787.dmg, available from the Epson site. Once you've installed them, restart your Mac.
Go to your printer prefs pane and delete any old instances of the printer in the added printer list. Then click the add button ➕ and wait for the list to populate. Depending on how the printer is setup for networking, you may see several choices for the 4800 -- my preference is to use the EpsonNet utility and let the printer get an IP address through DHCP (if you're using a router) and then use the IP instance of the printer. If connected by USB or FireWire, you may only see one choice. Use the "more Printers" button in Print and Fax if you don't see it, and choose the connectivity you have in the dropdowns.
Once you have it chosen, you should see Epson SP4800 in the "Print Using..." Dropdown. If you are seeing GutenPrint drivers, you may have to restart the machine if you've installed the Epson drivers.
