I'm in the same boat as you. Looking at a DIY whole-house A/V distribution retrofit, that doesn't break the bank too much.
One interesting avenue I'm considering is using i-devices for my controllers (iPod Touches, iPads, etc). While I generally prefer real buttons, particularly for channel surfing, it's becoming hard and harder to discount the ton of apps available for home automation, etc. One of the items that really draws me towards iPods is the Sonos app. I've decided on Sonos for audio distribution (their app is pretty impressive BTW), so combing the rest of my distribution and automation needs seems like a logical direction.
Looking further, I found some pretty interesting universal remote apps. RedEye in particular has piqued my interest. The interface functions quite similar to Harmony remotes in that it uses 'activities' as the workflow instead of simply switching between components. The hardware currently comes in two flavors; the primary unit is an IR blaster (basically 360 degrees) that communicates with the iPod via WiFi, and the RedEye mini physically attaches to an iPod for local-only IR duties. The former functions similar to an RF universal, while that latter acts as a traditional IR remote. I believe activities can use both, but I need some more details.
The great thing about the main unit is that it remembers 'states'. For example, if you do an activity that turns on your cable box, and then switch to another activity that also turns on your cable box, it knows it was already turned on and will skip that step! The problem however is that RedEye is meant to be a single user blaster. A given RedEye WiFi unit can only be in one activity at a time, so if you have two iPod's connected to it, they will both display the same remote UI. In other words, while it can control a centralized distribution setup, it can't really be shared. Granted you could get around that by having two RedEyes together (or I should say 1:1 with the amount of users you expect), but then you'd lose state awareness.
While communicating to the company via email, they mentioned a rack-mountable model with RS-232 and IR emitter jacks is in the pipeline. My understanding is that this is meant to support the use-case we want - multiple users sharing devices. Assuming it handles state awareness across users, this may be exactly what I'm looking for. I'm in the process of getting that last question (amongst several others) answered. I'll post when I have more info. Let's just hope it isn't too pricey