On the other key differences:
- Shorter lifetimes is actually an advantage, since it reduces the risk when your keys are compromised. Revocation is a mess, the only way you can be sure that a certificate can no longer be used is when it's expired.
- No wildcards is an advantage too, since you can give each service its own certificate and if one is compromised, the others are fine. If you're using an organization-wide wildcard cert, a compromise is much worse.
- Limited flexibility - "you must have root access to your servers " is factually incorrect, the automated Let's Encrypt client is optional and you can request a certificate manually.
- Limited support - why would I need a SLA for a certificate, anyway? The OCSP servers?
- Management difficulties - while this is true now, the automation enabled by Let's Encrypt is likely to facilitate management, not the contrary. I'm currently working on a Puppet module which will automatically provision certificates for web servers, something which used to be much harder.
- Build Trust with Purchased SSL - how do I increase trust by using a OV certificate? It's not like an average website user would look up the certificate details, and there's no functional difference between a OV and a DV certificate.
> The levels of encryption, validation, and trust that business and commerce websites require are available only with purchased SSL.
Unless you're talking about EV certificates, I don't see how. There's no "level of encryption" which isn't available with a free CA, and the additional validation and trust do not matter unless it's a EV certificate. Even an EV certificate does not protect against MitM. The real answer is key pinning.
As a Namecheap customer, I'm disappointed by this blog post. It reads like an attempt to spread FUD about free DV certificates. I initially became a customer because I read good things about your business ethics, but this makes me question my choice.