yes, quite a few people have been reporting this issue (it's mentioned in a recent scale issue thread)
horizontal scaling doesn't work smoothly & for some people (me included) the character sort of goes blurry/vibrates/shakes somewhat when it is walking (all other animations & character animations work nice & smooth mind - everything plays as it should in the editor animation previews too)
I think the walk cycle system needs replacing (David would like to replace it at some point but currently he doesn't have time to work on it, as he's busy with other - more important - things on the to do list at the minute -hopefully, he will find some time to sort it out at some point as he has some good ideas for making it more realistic too
)