Most insecure passwords don't use mixed case anyhow (dictionary lower-case words), so I fail to see how this is making them much less secure. In fact in terms

Most insecure passwords don't use mixed case anyhow (dictionary lower-case words), so I fail to see how this is making them much less secure. In fact in terms of relative impact, this has a much greater impact on "secure" passwords (in this case, I mean ones that are a random jumbled set of mixed case letters and numbers). That's only really because it significantly reduces the range of the first character.