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This works great for the sort of closed source programs Valve is targeting to market for. However as an end user it probably best to not think too hard about the implications of a stable runtime. Because in short "stable" implies "out of date" I think steam's newest runtime is Ubuntu 12.
Now like I said, as an end user this does not matter, your goal is to get the final program, you don't care about the runtime. and as a developer you may be slightly horrified, but in the end it is a relief to have something fixed you can target instead of the horrible shifting sand that is the normal Linux experience.