The problem with Remote Buddy in a browser is that it is limited to pre-defined controls:
For Sling.com, since it is a web interface and not a program per se, you need to have UI control (move mouse pointer, click on the remote control buttons, etc.) in order to control it.
However, if Remote Buddy's "Virtual Mouse" control does what it says (scroll to the bottom section of the above link), then you should be able to use that to dynamically interact with the Sling.com web interface (i.e., move mouse pointer over and click remote control buttons) - likewise with the "Virtual Keyboard" (login to Sling.com). It's not as elegant/intelligent as a remote control of iTunes or the non-web SlingPlayer for Mac app, for example, but it should still allow you to use the Sling.com remote...
Myself, I use the Keyspan IR Remote and the software that it comes with, which lets me move the mouse pointer and click/double-click anywhere with the default install settings right out of the box. Without being able to move the mouse pointer and click things, as if you were using a mouse, then you'd have trouble not only with Sling.com within the browser, but also navigating other websites and web-based interfaces with it as well.
Although you lose HD quality, you can still continue to use the SlingPlayer for Mac app to view your Slingbox (I have no choice but to use only that, since Sling's plugin download page has been out ever since I clean installed OS X on my laptop recently). Sling Media has stopped developing the desktop/dedicated player for Mac (which is why they're telling Mac users to use Sling.com with the fake update alert), but it still works as it always has, as of OS X v10.6/Snow Leopard (that may change if OS X v10.7/Lion, or some other future version down the line, does something to break it).
Thank you for the response.
I was afraid that was the only answer. To say that scrolling the cursor around to find proper buttons is a "less elegant" approach is an understatement. From across the room, it's nearly impossible to do this with any sort of repeated accuracy, especially when controlling a typical DVR, skipping commercials, etc.
My reason for purchasing the Keyspan remote plus Remote Buddy was to have a dedicated button for each task I do frequently when I watch: vol up, vol down, skip forward, skip backward, menu, up, down, left, right, mute, etc. So now we have a better picture with the web based client, but we lose all the device-addressable control. I would argue that the modern day process of watching TV requires BOTH for a good user experience. And now, to continue using SlingPlayer Mac (which is the only way to get both), I have to continually deal with a software upgrade pop-up, asking me to update to something that decreases functionality, effectively diminishing the TV experience.
In my opinion, this is a tremendous oversight from the developers of watch.slingbox.com.
The real oversight is keeping the Mac player a 2nd-class citizen.
As someone with experience in web technology, I can see why this would be difficult; however, someone could probably build a Firefox extension that might help, but I wouldn't hold my breath.
The little bit of good news I can offer is that Sling says on the landing page for the update that this annoying false notice is temporary and they're just doing it to let people know that the Mac player is no longer being developed, and to try to get people to use the web portal insetad. So, eventually the update notice will stop and you can watch on your Mac with the SlingPlayer app in peace...
I just noticed this while searching another issue:
Apparently, your remote may work if the web player is set to fullscreen. Read the above for more tips on how to figure out the keyboard commands to set for your remote if they're not already correct. It may not work with Remote Buddy, but I recall being able to configure different "sets" of commands to the buttons on my remote last time I set it up (and I'm not at home to try it right now either - not until Christmas).
Either way, might be worth a shot...!
Let me know.