Losing the GIL strictly makes the language strictly more flexible. Previous GILectomies tanked performance to an unacceptable degree. In single-threaded code, this one is a moderate performance improvement in some benchmarks, and a small detriment in others -- which is about as close to perfect as one could expect from such a change. That's why people are excited about it.
At a higher level, Python is getting serious about performance. But this gives both flexibility and performance.
At a higher level, Python is getting serious about performance. But this gives both flexibility and performance.