Depends on your usecase and preferences, I guess. I have a dedicated PC connected permanently to my TV and amp. During the day I use it listen to webradios, without turning on the TV. For this, I just press play on my remote, and it's on. When I leave, I just press stop. You get the idea.

In the evening, when I watch a movie, it's just my personal preference - I like to kind of disassociate from computers. A remote helps. Also, being able to change the volume blindly, without looking at the remote is something that other interfaces have yet to emulate.

Of course not saying that everyone should use it - if a mouse is better for you, go for it, what do I care :D But remotes definitely have a place with today's HTPCs also IMO.