SEO shouldn't be hurt (unless of course you are running the same site at both swomb.at and swombat.com), however with that said you won't get the seo boost that

SEO shouldn't be hurt (unless of course you are running the same site at both swomb.at and swombat.com), however with that said you won't get the seo boost that .com gives. Another thought: swomb.at could be considered worse than say swombat.at as it is using the TLD to complete the word but I may be completely wrong in that case.