I'd like to hike Mt. Sabyinyo (on the border of Uganda, Rwanda, and DRC). Is it better to start the hike in Uganda or Rwanda. Are there any logistics that I need to be aware of? Any necessary permits or transportation issues?

As far as I know, all volcano climbs in Rwanda are inside the PNV (national volcanoes park) and organised by the Rwandese tourism and national parks office ORTPN. I don't think you can do this on your own without a permit. See www.rwandatourism.com.
Normally, ORTPN offers two volcano climbs for tourists:
- Mt Bisoke: 1 day hike (5 or 6 hours up and down), 2400-3700 meters
- Mt Karisimbi: 2 days hike, 2400-4500 meters, spend one night in a tent in the forest.
If I remember well, Bisoke is about 75 USD and Karisimbi about 175 USD, not sure but i can check if you want. I did both climbs.
In the past I have heard of rumours ORTPN would open up also Mt Muhabura for tourism, but I think there is nothing concrete yet. I have never heard of Sabyinyo hikes in Rwanda. Because of its shape, Sabyinyo is probably the most difficult volcano to climb there.

You don't need any visas or permits, except to Rwanda or Uganda, depending on which side you enter the mountain from (it is in parks in both countries, you only pay entry on one..... uganda is cheaper.)

I did it from the Uganda side. You just need to get to Mgahinga NP and organise a guide at the gate. We hitched a ride from Kisoro to get there and walked back.

I should have mentioned that we didn't make it to the summit because the weather turned bad and it was hammering down by the time we reached the bottom, but strangely stopped shortly afterwards. I don't remember it being that hard, although we didn't reach the really steep bit nearer the summit, and I can't remember how long it took. Couldn't have been that long because we walked for two hours back to Kisoro and it was still light.

May I ask you what kind of equipment did you have? It is not a simple hiking mountain, or is it? What technical skills does it involve? Thanks for your reply.

It's a hiking mountain, no special equipment required. More details here:
http://www.uwa.or.ug/mgahinga.html

I don't suppose any one remembers how hard it was? We've done a lot of hiking in the Canadian rockies, some fairly steep elevations but nothing like the pictures I saw of Mt Sabyinyo with rickety looking ladders. Is there a lot space on either side of the ladder? Is it gradual? Or am I going to have my heart in my stomach the entire the time?
I'm trying to get a better feel for what I'm getting in to before we book it....