RE: Is this a good field box set?
I think that is a good Starter setup. Now it depends on what engines you want to use in the future and you will get a different box.
The lead acid battery here is sealed and safe to use. The acid is more of a health risk, but it is contained and you had to use excessive force to get the battery to break open.
I have a huge box on wheels with a small car battery, this provides enough amps to run the starter for the bigger gassers and I charge in only 2-3 times a year.
It also hold all kind of tools and spare parts, since the field is 40 minutes away I don't want to run home to get some screw, servo, battery if needed.
Every rc pilot I've seen has a field setup, you'll get lots of different opinions here.
I have bought from this seller on e-Bay and would do it again.