"Support" is a bit of a stretch. The 520 is long out of warranty and uses the older software. You can still email codes to [email protected] to add commands. It still does share the same database as the latest remotes. However, I would avoid it since the vol and chan buttons wear out quickly on the 5xx series (probably are already worn out if you're buying used).

The 650 is still a current model and uses the latest software. I would recommend that one over the 520. The buttons are also more reliable in my experience.

If you're not married to the idea of a Harmony, the Nevo C2 is a far better remote and far cheaper at $16 on ebay. It does 18 devices versus 8 on the 650, has a bigger/better display with more functions and can import pronto hex codes directly, no support required. The software is also much better. I've been using them for years and have about 20, so I know just about everything there is to know about them. I also have a couple of 650s and 520s in my closet, unused, if that tells you anything.

Here's some more info on the Nevo:
[Link: hifi-remote.com]

and an ebay search:
[Link: ebay.com]