Tvheadend

The purpose of this post is to document how after much trail and error I was able to get XBMC to play live TV from my HdHomerun via Tvheadend. I hope it is useful for someone else. I make no claims that it is the only or even the best way to go about accomplishing the goal, only that it worked for me. Please note that this is a complete summary according to the best of my recollection. With this in mind further note that it is not beyond me to possibly have omitted some steps that I either forgot or consider so obvious that they do not need mentioned. Please provide feedback if you feel some added steps ought to be included and I will do my best to update the OP accordingly.

Install XBMC with TV/DVR Support:
sudo apt-add-repository ppa:alexandr-surkov/dharma-pvr
sudo apt-get update
sudo apt-get install xbmc

Install Hdhomerun software:
sudo apt-get install hdhomerun-config hdhomerun-config-gui

Make sure the HDHomerun is found:
hdhomerun_config discover

Output should read something like:
hdhomerun device 103194EA found at x.y.z.a

If it doesn't check your firewall(s).

Install tvheadend:
sudo apt-get install tvheadend

Make sure tvheadend web UI works and set up users:
open browser go to: http://tvheadendserver:9981/
click "Configuration" tab, click "Access Control" tab;
set up 1 admin user (all rights);
set up 1 xbmc user (all rights except admin);
optionally limit access to local host by setting both prefixes to 127.0.0.1/32.

Stop tvheadend:
sudo service tvheadend stop

Install other needed stuff (dvbhdhomerun driver):
sudo add-apt-repository ppa:tfylliv/dvbhdhomerun
sudo apt-get update
sudo apt-get install dvbhdhomerun-dkms dvbhdhomerun-utils
sudo service dvbhdhomerun-utils start

Set kernel module to load on boot:
sudo echo dvb_hdhomerun >> /etc/modules

Config dvbhdhomerun:
sudo nano /etc/dvbhdhomerun
change settings to fit your config as described in file.

Restart:
sudo reboot

Start all the little helpers:
sudo userhdhomerun -f
sudo service dvbhdhomerun-utils start
sudo service tvheadend restart

Finish tvheadend config:
open browser, go to: http://tvheadendserver:9981/
click "Configuration", click "TV Adapters"
Select an adapter in dropdown list;
Check Autodetect muxes and Idle scanning;
optionally change the adapter name;
click save;
Click Add DVB Network by Location and select yours;
The Status display will now change to show how many Muxes there are and how many more need scanned;

Set up XML Grabbing:
While the muxes scan go to: http://www.schedulesdirect.org/ and register for an account;
Log in, click "Add a new lineup" and follow the prompts;
Sign out;

sudo /usr/bin/tv_grab_na_dd --configure
follow the prompts

sudo cp ~/.xmltv /home/hts/
click the "XML TV tab";
Click "Enable debug output" (the little gear at the bottom right);
Select "North America (Data Direct)";
set desired grab interval;
check "Enable grabbing";
hit save;
wait for the XML Grabber to do its thing (about 2 minutes), you will be notified it is done in the debug window;
go back to "TV Adapters", with any luck your muxes awaiting initial scan will now be down to 0;
if so, continue below, if not have a cup of coffee or something and wait till theyre done;

Map DVB Services:
Click Map DVB services to channels
Click the "Channels" tab;
for each channel double click in the XMLTV source column and match the channel to the corresponding source;
Save your changes and close the browser.

Config XBMC:
Start XBMC;
go to System -> Settings -> Addons -> Installed Addons -> PVR Clients -> Tvheadend HTSP Client -> Configure;
Make changes to suit your setup;
hit ok;
hit enable;
escape to main settings screen;
select Live TV;
check enabled;
escape to XBMC main screen;
select Live TV and verify it works;
you are done.

Closing note:
I have to repeat the "Start all the little helpers:" step after each reboot. Yes, they could be included into some sort of startup script but no, I could not be arsed to find out how. If anyone cares to share, please enlighten me

For reference, I am running the following specs:
Acer Revo 1600 stock, except upgraded to 2gb ram
HTS Tvheadend 2.13
Dvbhdhomerun 0.0.9-2
Lubuntu 11.10
XBMC Pre-11.0