Temperament! Weims are HPR's - basically a high spirited working dog, headstrong and can be sharp with both humans and other dogs as can many HPRs (continental breeds). Working Springers, and some show lines too, are inclined to be the same. Springers have a reputation for being destructive, high spirited, and are obsessive workers as well. So you are doubling up on high spirits, obsessivenes, plus throwing in a possible temperament fault, not to speak of any health issues. Personally I wouldn't cross breed anyway - my opinion is that there are plenty of pure bred dogs where you have a pretty good idea what you are going to get in health (the KC have laid down the health checks required for all breeds - readily available on their website), temperament, size, shape, ability without mixing them.
Contrary to public belief, for instance, you can't get more labradoodles by mating a doodle to another doodle - you just get mongrels because they don't breed true to type - even 30 years down the line from when it was first done by supposed breeding experts with the Guide dogs for the Blind! And also contrary to beliefs they aren't all hypoallergenic either! There's a chap on here who has a rather charming doodle, and he is absolutely lovely but he has a heavy coat.
Sorry, a particular soap box stance of mine - rant over.
