I know I don't post here much, and when I do it seems to be only to complain, but I look at that as being a testament to MC, in a positive way. Overall it just works, no tweaking, no troubleshooting, I just use it.
That said, a true client/server architecture is something I've been wanting, almost since I started using MC. If you want to know what I mean by "true client/server", just look at SageTV, IMO it's a model of what a client/server media system should be (if not a model of what a music system should be :p).
What I mean, is I have
one and only one instance of the program that contains the database (the server), and all other devices interact with that, one singular database (clients). There's no keeping databases synced, not messing with where you do stuff, you can do whatever you want from anywhere.
Now you can get probably 75% of the way there with MC's current media server functionality, and that is what I currently do. However it's that remaining 25% that I really miss at times. My MC server is the same as my SageTV server, it's a Win Server 2003 box with almost 2TB of space, and between Sage and MC it manages all my media on that box and another 1.5TB NAS. This is a headless box, stuck in the corner of the utility room in the basement. There's no keyboard, mouse, monitor, optical drives, nothing.
What this means is that I must (I want to as well) do all my ripping on my desktop upstairs. That part I don't mind, but where it gets to be bothersome is that it seems (even with Auto Update enabled) I have to RDP onto the server and coax it into updating it's database with newly ripped files.
But that's only a small annoyance, I don't do it that much. But what I really miss, is the fact that changes to playlists, creation of playlists, changing of ratings, etc, all must be done on the media server to stick. For example, probably 75% of my listenning (if not more) is at work, via MCs awesome transcoding. There are times (eg after I rip a CD but haven't yet rated it) where I'm listenning at work and think a rating should be changed, and I can, but it doesn't get stored to the database. Likewise, sometimes at work I'd like to create a new smartlist, or update a current one, but again, it won't stick. And at work RDP is not an option, first because I don't want to get into that at work, and second because it's impossible (appears to be blocked offsite).
Contrast this with SageTV, where any client is as fully functional as the server. You can schedule recordings from anywhere, mark stuff Watched/Don't Like, change import directories (from the server's perspective), and yes delete. And if you look around the Sage forums, while user control is a requested feature, it's far from being cried for. The lack of access control doesn't seem to be a problem there.
However if it is an issue, maybe the solution could be as simple as a flag on the server to enable/disable client write access. Or at least, maybe that would be a closer compromise between those who want the clients read only, those who want write access from clients, and those who don't relish the idea of implementing full user-access controls