Hi, I asked the same question in a WP Central article and got the below response. Hope this helps.
Your question has 2 points that need to be cleared up:
a) ANY product/firmware update is risky. ALL of them. Even the ones that come OTA from your carrier. IT is an inherently risky operation since you basically flash the phone's ROM memory. In principle everything should go fine... but this can't be %100 guaranteed. Because of this...
b)... the dev preview is no better/worse than the carrier OTA. In fact, the dev preview is the EXACT same build you'll get from the carrier. The only difference is the carrier might make some adjustments to their network or add some firmware bits (you don't get firmware bits through the dev preview, just the newest RTM OS version). That said, the dev preview name is very misleading (surely how carriers wanted it) because it suggests some sort of pre-access, as in pre-finished, as in beta. This is %100 NOT the case: the versions you are getting are fully finalized (well, until the next update, no software is ever really final).
Therefore, having those 2 points into account, you can conclude that installing the dev preview builds is no different from waiting for the carrier. Once the carrier decides to push the update OTA (which takes them forever and they claim it's for testing purposes, when most of the time the REAL reason is that they don't want people with updated phones that work better as this can push them to ditch the phone and get a new one with a shiny new 2 year contract plan continuation) the OEM will add firmware to it. Even if you participate in the dev preview program you'll get the firmware updates once the update is "officially" available through carriers. You won't get the OS update (since you're already running it), just whatever else is released that you don't have yet.
Dev Preview is a WIN no matter how you look at it. It's designed to bypass evil carriers. This is the one advantage that Apple has over everybody because they were first to the smartphone market and thus got to dictate many conditions. Dev preview is Microsoft's way of doing the same thing, just like Google does this in their Nexus phones that bypass carriers.
I've done about 4 updates through dev preview by now, never had any problem because it's inherently the exact same process as waiting for the carrier, just earlier. Do it. You won't regret it and your phone will be more fully featured and, most importantly, more secure against threats.
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