With Miyagawa's cpanminus (or as I like to think of it, cpantiny, but hey it's his module) now officially the New Shiny of the moment, the same old arguments are resurfacing about less is more, and worse is better.
And the great wheel of opinion circles again.
Rather than bother commenting on cpanminus itself (I suspect many could guess my opinions) I thought I would add some caveats to the praise, that hopefully can help you identify and engineer your own equivalent successes.
1. These "subset" modules are truly successful only when you make the accuracy trade offs worth it.
Thus, the installation must be effortless, the user interface must be super-simple, zero-conf is an absolute must, and the module must succeed in all those niches where the "real" application is too hard, too big, or too clumsy.
If your accuracy is going to suck, NOTHING else is allowed to suck.
2. As I hint about with "real" these subset modules work best when they are an alternative solution, not the only solution.
If you are inaccurate and the only solution, you are an annoying limitation.
If you are inaccurate and an alternate solution, you are handy because you create a kind of user-pays situation. Simple people with simple use cases get a simple solution. Hardcore people with hardcore needs get a hardcore solution.
So if you want to make a small solution, it has to be a subset of something larger that works better. It can't be the only solution.
3. 99% is a just a marketing number, but the real number does matter.
Why? Take a look at the Heavy 100 index (http://ali.as/top100/") and you'll notice that many major and popular CPAN modules (like, say, Catalyst) have more than 100 dependencies.
With a 99% success rate (using stupidly naive "statistics") every single module on that Top 100 list will fail to install. In a large system with lots of recursive dependencies, it doesn't take much for your install count to grow to 20 or 50 or 100 dependencies.
So you need to be sure about WHICH subset you want to support, so you can be sure what percentage you REALLY need.
For example, despite all the work to support it, there is only one single module currently using Bzip2. Would it be worth it to remove bzip2 support entirely from the CPAN and help that author to convert? Probably.
The biggest benefits of these alternate solutions are often not only to do what they do. It's to demonstrate what is possible, pushing the competitors to do it as well.