Really depends on what you need it to do.

If you plan on using a captive portal with a custome portal page or a custom web page for the portal, or if you want ongoing statistics on usage then yes you need the computer on and logged in at all times with the eap controller working. For the aforementioned portal setups you also need to be sure the folks logging in are on teh same vlan as the eap controller.

Otherwise you can set it and forget it, just be careful, if you open the controller and shut it down while it is in the middle of doing something to an AP (even if it is just garbbign current stats) it might wipe the AP's configuration and you will have to fire the controller back up and let it reprogram it

Feel free to post back with details on what you want it to do and I'll be happy to let you know, i just spent the last few weeks learning the power and limitations of the eap's and thier controller software.

Thanks for the quick reply! Actually we don't need statistics and portals.. We just need our WiFi more.. stable. Currently we have a bunch of airport extremes (configured as AP) and we've had some mixed experiences.. The problem is that we have a 4 storey building with several closed offices and we really need a good quality WiFi throughout the entire space. We're thinking not only on replacing the current AP but also on adding some more to have a good coverage in all floors and finally have some decent Skype calls on WiFi (nowadays only possible through Ethernet cable).Best, Gonçalo

What a fun coincidence, this install was to replace the setup in a hotel made up of airport extremes and airport expresses. It's a pretty universal truth that home class is not suitable for business :) One thing with these AP's the radio's are VERY powerful, I can pick up a -80 RSSI signal from 400' through 3 buildings and zero line of sight. I had to turn the radio's down to 10dB to avoid clients with weak radios (like cell phones and tablets) from connecting to an ap that they could not talk to. these are pretty nice units overall.