I did have some issues with my current internal dvd burner and going to replace it, an external usb dvd burner came to mind because it would free up one sata port for an additional internal harddrive.

Only, how reliable are external usb dvd burners? Speed is not important for me as I always burn at the slowest speeds, what matters most to me is compatibility with all kind of dvd players. My dvd's end up on all kinds of dvd players and it's very important that they play without a problem. I"m not so sure whether these ext burners that connect through usb interface are as reliable as internal ones?

Can anyone here share their experience?

External burners are exactly the same hardware (but in an external box with PSU and interface) as you find in internal burners. Reliability of the burner part must therefore be the same.

It is true, the external PSU and interface might fail, but you can more easily replace the bit that's failed - assuming you're OK with taking these things to pieces (screwdriver?).

You can also position it where you want (e.g. on a desktop, rather than in a tower under the desk?)

Thx Martin for your answer, a worry of mine was that the usb connection was not fast or reliable enough feeding data to the burner but I guess since I burn at very slow speeds that shouldn't be a problem.
I'm not very keen on external devices that rely on how fast data can be send, I used to have a external box with a ide harddrive build in and that one had a firewire connection. It caused me nothing but connectionproblems.