I just rewatched 'Relics.' A lot of the Dyson Sphere stuff still looks great, but they reuse some standard angle shots of the Enterprise flying toward it/around it [i.e. they just cut and pasted one of the stock Enterprise shots onto the background]. They also reuse a shot of the Enterprise flying out of the Dyson Sphere.
They could also correct an oversight - they transport Geordi and Scotty off of the transport ship with its shields still up. This would be easy to correct, as they could show the shields being shut off prior to their being transported.
There's a horrible looking blue/green-screen effect when Scotty first walks into the Holodeck [and when he leaves] - again, very fixable now.
I think Phil Farrand mentioned this last one in his 'Nitpickers' book - given the size of the Sphere, I'm not sure you'd be able to see the actual curvature of the structure in one of the early shots.