Well, I've never had any issues with my 4500s accept for one build that was quickly fixed by D-Link. Other then that, most all of the FW versions were good. There was a lot of issues however after I came to the boards here, I soon learned that most of the problems stemmed from user mis-configurations or there environment and surroundings.
I've tested many versions and they all work very well and are very stable. The 4500 is still a great router minus the fact that IPv6 wasn't going to be supported and the WiFi was not simultaneous dual band like the 825 and newer model routers are now days. These were only a couple of things that some users wanted however over all, Theres only been a few newer routers that can hold a candle to this great router. Ya all the new WiFi standards are out today. The 4500 could be upgraded using AC Access points if one were still wanting to use the 4500 as a router only.
With all the newer gen routers that have arrived and the new features and bells and whistles, thats probably driving down the value of used 4500s, and has the 4500 ages, it will be still a good router, just given enough time, will eventually become out dated and not useful at some point in time.
Get what you can selling it. If you don't think you can or can't find a good home for it. Keep it and use it as a spare AP or back up in case your new fangled AZ50000000 WiFI godzillabyte router takes a dive, you'll have something to fall back on.
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I still have my 3 4500s, hehe. One still in the box un-opened.