I tested the 500 with Fios TV and had to use the component connection from my cable box to the Slingbox; the HDMI input on the Slingbox was rendered useless. However, I did use the HDMI output on the Slingbox to access the unit's menu system on my TV, as well as the new SlingProjector feature (see below).
The Slingbox 500 offers AirPlay-like functionality the company calls SlingProjector, which makes it possible for iOS devices and Android phones to stream photos and self-shot videos from the handheld to the TV screen at the touch of a button. And because the Slingbox uses HDMI passthrough, it can share an input on your TV -- so if you activate the SlingProjector from your phone, the Slingbox "hijacks" the DVR input for the duration of your presentation, and then just flips back to the original programming when you're done. (Note: due to the nature of my setup, I ended up not using the HDMI passthrough, but I did use the HDMI output).
If you're an Apple TV owner and have iOS devices, the SlingProjector will duplicate a feature you already have. But it is nice that the feature supports Android devices. I tried it out with a Samsung Galaxy Note 2 and an iPhone 4S. In both cases, the feature worked as advertised. I simply tapped a little icon on the screen (just as you do with AirPlay) and my images and self-shot videos played on my TV. The video playback was smooth, too -- no stuttering or dropped frames.
On the back of both of the new Slingboxes you'll find a USB port. Right now, that port doesn't do anything and is reserved for additional features. A subsequent update is slated to make it possible to play USB-based digital video on the Slingbox 500, as well as sync videos and photos from a smartphone to the connected USB drive -- a process the company will call "SlingSync." Both features are currently slated to arrive in "early 2013."
Like the Slingbox 350, the Slingbox 500 is an excellent device for streaming video. It was easy to set up and worked smoothly in our tests, offering impressive video quality when streamed inside and outside the home.
That said, the Slingbox 500 is fairly pricey at $300 (list), so you should only choose it over the 350 if its extra features are important to you. While the SlingProjector and HDMI connectivity are nice bonuses, the real key for me is the Wi-Fi. I happen to have an Ethernet connection available to me where my AV components are located, so I'd be fine with the Slingbox 350, but if I didn't, I'd bite the bullet and spend the extra $100 or so to get the 500's wireless capabilities. I wouldn't necessarily be happy about it, but the HDMI and SlingProjector features help make the price jump a little more palatable.