Didn't expect much from this but the kids are good, Merlin (both old and young) is a delight and it's actually rather corny fun. If you expected it to be anything else, why are you watching it?
Only effect I thought weak was the one for 'MorganaDragon' and the rest are up to par, in the main.
Story isn't overlong, unless you can only tolerate cartoons. Neither the best, nor the worst film you'll see.
Give it a go. Avoid preconceptions. If you're disappointed, you simply have no soul. Particularly if you can't warm to Bedders immediately.