I am giving this at best a 3/5 stars.
Cons
1. It is hard to keep it moving as it is only using rails and doesn't use powered rails w/ redstone torches.
2. The storage system is rather small with at most a combined 3 double chests of storage which is a fair amount but it is also a 5x5 mining machine so that fills up pretty quickly which stops the machine.
3. Beside the fact of #1 it wouldn't be a massive issue that it is using rails if it was able to be pushed manually by the player, as far as I can tell it can't and if you remove the glass trapdoors to do it, it disconnects it and is not a minecart contraption anymore.
Pros
Even with all those cons it still does work for a fair couple blocks...................(before needing to be reset and get it moving again)