It's not necessarily about the pace. Some 0.x software is more feature complete than other 1.x software. It's not possible to compare versions between different pieces of software to infer anything meaningful about how much work went into them.
To give an example, it took VLC a long time to reach version 1, yet even in its 0.x releases it was amongst the best video players available (in terms of features, performance and stability), better than many other closed-source competitors with higher version numbers.
In other words, aside from libraries and programming languages (where major version numbers do have extra significance), version numbers are only loosely coupled to software quality.
To give an example, it took VLC a long time to reach version 1, yet even in its 0.x releases it was amongst the best video players available (in terms of features, performance and stability), better than many other closed-source competitors with higher version numbers.
In other words, aside from libraries and programming languages (where major version numbers do have extra significance), version numbers are only loosely coupled to software quality.