No first hand experience here, but I did look into them awhile back. I was unimpressed by the way they used the space, seems like they wasted a lot. Advertising that they have an escape hatch on the other end is kinda dumb, in my opinion. The main blast door looks super strong, but the hatch would be easy to breach if you found it, and anyone who has watched the videos would easily find it.
On the plus side, you gotta like a place with its own NBC filters.
I would imagine you could build your own for about 1/2 the cost, and it would be perfectly suited to your needs. If I was gonna do it, that's the way I would go.