i live in austria and i would recommend to not register any .co.at โ they are worthless. to be honest i also wouldn't recommend to register any .at domain. traffic is at least 10 times smaller than with .de-domains. the amount of .at-keyword-domains with value is much smaller than in germany. the .at-key has to be much stronger compared to the .de-counterpart to have any value. and don't forget that we are a german-speaking country, so probably 95% of the valuable .at-keys are in german language.
it's almost impossible for me as a german speaking austrian to register any valuable .at-domains, so i think it's even harder for non-german-speaking domainers. ALL the valuable names have been registered a long time ago. in case of a drop, all valuable names get catched by professional drop-catchers like realtime.at.