Huh? Not sure the what you're trying to compare here... iCloud is an email provider, not an enterprise server like exchange, nor an email forwarding provider (like Blackberry)... you're comparing Apples to Fortune Cookies to Pickles. Completely different things.
I am not even sure what your point is in responding? Are you saying iCloud is more reliable than exchange? Or are you saying Exchange isn't as reliable as Blackberry (which sits inside a firewall and feeds from an Exchange server directly)?? Your comments don't make sense. Since you commented on BB email for personal email, clearly you're not referring to a Blackberry Exchange Server integration... so dunno what you're trying to make with those comments.
I read through your comments again. It's clear you're not understanding the difference between a email provider, an email server platform, and the methods email gets delivered. Because you mention personal email, then blackberry (which only pushes email be it corporate or personal), then bring up an actual non-enterprise class email service (iCloud).
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Huh? 6.0.1 to 6.0.2 was 48 days! 18 days and you're worried?
http://en.wikipedia.org/wiki/IOS_6#6.0