The Mag 1 features a well finished steel frame, with a good quick-release clamp that holds the bike securely. The fixed resistance unit, on the other hand, is less substantial, with a flywheel much too small to keep much inertia when riding.
Right from the off it's clear that the ride feel of the Riva suffers because of the small flywheel; there's very little compensation for the dead sections of the pedal stroke. The unit produces enough drag for a reasonable steady session, but it doesn't cope well with intervals (the lack of inertia makes recovery spells uncomfortable) or standing up (there simply isn't enough resistance) so it's pretty limited in terms of the workouts it can offer.
It's fairly light and small, so if you just want a turbo to chuck in the car for race warm-ups it might fit the bill. It's cheap, so we weren't expecting miracles, but the Gist Magnetic at only £20 more, is simply in another league - it's that unit, not this, that scores the points for value.