Assuming the welds are good, that thing will probably be nigh indestructible. 4130 CrMo is about as bomb-proof as it gets. Heavy, though. Just make sure you use Frame Saver to keep it from rusting out, and drain it if you ride in the rain. You'll also probably need to face the headset, BB shell, and disc mounts, tap the BB threads, and check the alignment on the rear-end before you build it -- I doubt that their QC is very good. But safe... Probably.
Nashbar is quite good at accepting returns. If there's a problem with the frame, call them first and ask for a pre-paid shipping label or you can ship it back and they will usually reimburse you for shipping costs.
Nashbar is part of the largest chain of bike stores in the country (Performance Bike / Supergo / Nashbar) -- you don't have to worry about them not taking it back. But if it's only a bit out of alignment, it's not a big deal, most frames come out of the box a little tweaked. And since it's steel, it's easily fixed.
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