Requiring compatibility with the Firefly is like the time when my parents did a complete bathroom remodel, but required that everything match the bath mat that my mom already owned and liked. There might be an easier solution that you like even better.
Maybe. I've looked into (repeatedly) replacing my Firefly with something else. Not that I really need to, yet, but they've been discontinued and the one I have will break eventually. Nothing out there that I've found meets my (reasonably modest, I think) requirements:
1. Physical buttons.
2. RF, Bluetooth, or some kind of non-directional line-of-sight-only control.
3. Not a gazillion dollars (the Firefly was like $30 and is wonderful).
Keep in mind, I already own Girder, and already have everything programmed for it (including GMLs for MC and Firefox and everything else I use). It was reasonably painless to get it set up with my Denon and USB-UIRT as well. My main issues with it are that it is a bit crashy (it crashes maybe 2 times a month at random), and performance isn't super-good for IR-blasted commands. Otherwise, it works perfectly, and I know how to use it.
I do already have a nice wireless keyboard and two mice for my HTPC (an Apple Wireless keyboard, a Logitech mouse, and one of the sweet Logitech trackpads). The remote is what we use for most TV watching and controlling Theater View. And, it can turn everything on/off with a simple button-press. I use it to peruse the web sometimes too (I have a mod for Firefox that puts it into "mobile mode" so it gets iPhone compatible pages, and then you can navigate a surprising array of sites easily with just up/down/left/right/enter and escape).
I also do use a few iOS apps to control the HTPC (mostly AirMouse). The issues with this, for me, are:
a. There is an absolute FIRM requirement that ALL major HTPC functions (on/off/volume/mute and launching key applications like MC) MUST be accessible from a
single remote.
b. I like physical buttons on a remote. I'd probably get past this if it worked really well, but I really do like being able to control the system without looking, in the dark, by touch.
c. More importantly, I want something that "belongs" to the HTPC. My wife and I both have iPhones, and we have an iPad, but they're mine. When we leave, they leave. I want something that visitors can use when we're not at home.
So, to meet C above, I'd have to essentially buy an Android or iOS device specifically for room control. Likewise, the Harmony remotes are all expensive and IR (they do have things you can do to make them RF, but they seemed clunky). Line-of-sight-only is an absolute dealbreaker for me. We regularly use the remote in the kitchen, at the dining room table, and all over the place. The WAF of changing this stuff is pretty low. I've had the Firefly (or similar setups) now for around 10 years. The WAF is high and backing out would be very, very difficult.
In a perfect world, I'd have an AMX or Crestron or something, with a nice custom-built control with Lutron controllers for the lights and the whole bit. But I'm not spending $30k on room control. I live in a little 3 bedroom Cape Cod house.