Last fall I needed to replace my Garmin 510. I purchased the 520. I'm still not real happy with it but am getting used to it. In hindsight I should have tried the Wahoo RFLKT.
Just the Garmin UI to set up is a major pain in the ass. Using it on the road is a pain as well. The buttons are too hard to push and poorly located. Some settings that were simple with the 510 are difficult with the 520. No touch screen is a hindrance.
Garmin assured me that the warranty will transfer if I sell the device, which I still may.
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Sir Mark, Knight of Sufferlandria