Yeah, I've had experience with both good and bad swords. Things to watch out for are short/thin tangs and lousy steel. Tangs should be as thick as reasonably possible and extend through the pommel. Steel should be properly tempered with a Rockwell hardness of between 50 and 55 or maybe 60 depending on how the sword is used (cutting, cleaving, or thrusting).
Chris Poor's work is outstanding: http://www.armor.com/
(no connection - just satisfied with the work). The Steel Source
is a store local to me that stocks a lot of good stuff and also some cheaper stuff. The folks who run it are very good and if you tell them what you're looking for -- battle-ready -- they'll be able to direct you. Other sources like Museum Replicas
can be a crap shoot unless you're familiar with the quality of work that comes from a particular source.
What type of sword are you looking at?