They are a pretty good starter marker, and fast enough for what you can generally shoot at the start.
From the ones i've tried (was from the first batch/this might have been fixed) if you tilted the marker back, occasionally the ball would roll back away from the eyes, you could also get a similar result from running with the marker... i think the bolt was a little to far back though.
He might want to consider getting a PMR instead, they are not much more, (£20 ish) and are very very good... have four of these for the uni club and they all run wonderfly