Playing in sieges with a normal board shield now. Works fine, just have to watch out for arrows.
It broke about 2 times on me, once after getting kited by Tenne across the walls and taking loads of blows/arrows and once when fighting a guy with a GLB.
It's just slow. The heavy board shield is even more durable, but a bit slower and heavier than the huscarl shield with less!! coverage. You can't get hit in the foot or face when using a heavy board shield, but the same applies to the huscarl. The heavy board shield exposes your sides though, the huscarl still blocks arrows from the side.
The only real reason to take the heavy board shield over the huscarl is style.