I think I can guess at one effect, and that would be an almighty wheel shimmy ... that would probably take the plane apart after a few landings.
The shimmy from the tailwheel on a Citabria can give you a pretty severe shaking ... so I hate to thing what shimmy on a castoring main gear would be like ...
In practice, tailwheelers aren't so bad, just make sure you keep it all straight on landing, and you'll be ok ... there's a great point where steering down the runway with your feet suddenly becomes completely natural ... great feeling !