I would do a home-run installation, all the way back to the basement panel. Splitting a signal from one wire to as many terminations as you're likely to need is not a good idea. Since it's just about as easy to get four wires up there as one, I'd go home-run.

hatman

I would definately recommend home runs for the cable if you can do it easily - and I would suggest running two cables per room if you ever plan on using satellite for TV. For the data, you could get away with one Cat 5e and put a hub or router on the second floor. You can also do the same thing with voice - run one line to a voice distribution panel upstairs - and then run feeders off of that.

One thing I would be careful with - 1.25" doesn't sound big enough to me to run 4 cables, 4 data, and 4 voice lines. It is going to be hard to pull all of those wires through unless you use a structured wire - but given the number of rooms you have - you will need more than 1 structured cable. It might be hard to pull all of that cable at once - and you won't get it all through if you try doing them sequentially. I would recommend adding one or two more conduit runs.

I just got done wiring my house. I ran 3/4" conduit from the basement to each 2nd floor room so that I can home run a structured multi-media cable to each room. The structured cable has two RG6 and two Cat 5e and is 1/2" in diameter. If you did 4 + 4 + 4 - that is getting close to 1.25" just for the cable and you will need some wiggle room to pull it.

I would strongly recommend running a minimum of 2 RG6 and 4 Cat5e for each location on the second floor.

2 RG6 for possible dual tuner sat (or other usage like CCTV).

1 Cat5e for telco.

1 cat5e for ethernet (ALL conductors used for high bandwidth).

2 cat5e for HDTV audio/video distribution.

That 1.25" PVC is definitely not large enough.