A few notes about the route.
Part 1: National Cycle Route 3 up to Førde.
This is a route of contrasts that starts in Kristiansand and works its way North up to and past Førde. Much of the route up to Valle is suitable for families with children. Not in the sense that it is free of hills more that it is on quiet roads, with little or no traffic. Some of the quieter roads are gravel/grit which can be a little slippery in the wet.
From Valle to Haukeli the route follows main roads for much of the time. Cyclists are occasionally pushed off onto more minor parallel roads if they are present. There are some more strenuous climbs, up to Bykle is short but steep for example and on the other side of Bykle a loop away from the main road takes you up a very steep hill. The main road after the climb past Hovden consist of lot of long drags or slight inclines, taking you through a very open valley to the tree line. This only stops when you reach the fast deep descent into Haukeli. We didn't experience too much traffic on this section and only a couple of scary moments. Keep an eye out for vehicles containing distracted tourists, we had no problems from cars with Norwegian number plates.
Haukeli to Røldal is another kettle of fish altogether. The E134 between these two towns is the main road connecting the eastern and western parts of Southern Norway. Although Route 3 spends as much time as possible on old roads and quiet tracks (especially over the longer tunnels) cycling on the main road is unavoidable. The worst section, if I remember correctly was around Vågslid where the road twists and climbs its way uphill. There is not much you can do about a vehicle coming round a blind bend too fast and finding you plugging up the road slowly. Past Haukeliseter the cycle route leaves the main road for some time, first on a rough track past a small cheese factory (makes excellent cheese) then continuing after a short steep climb, on the old road which is lovely. Some of the tunnels are closed to cyclists and you are well advised to take the alternative routes when available.
The descent into Røldal is fast on the main road, although for part of it you are kept off the main road. Officially you are NOT allowed to cycle through the Austmannli tunnel. Rather confusingly, the 'Sykkelturer i Norge' overview map (2007 edition) shows the tunnel open to cyclists in both directions, while the excellent tunnel map on the Cycletourer website shows it closed in both directions.
I don't remember any signs banning cyclists from going downhill through the tunnel in 2008 and I couldn't find any near the entrance to the tunnel in 2009 when I checked. However, cyclists are definitely PROHIBITED from cycling uphill through the tunnel and clearly PROHIBITED from cycling downhill through the tunnel (Thanks to Jon at the Cycletourer website for that tip). Going uphill, (towards Haukeli) you have to take the old road that turns off the E134 just before the entrance of the tunnel, opposite a campsite. Going downhill, (towards Røldal) you have to look out for an unmarked left turn on a sweeping right-hand bend. Take care when crossing the road as traffic could be travelling fast in both directions.
The climb up out of the other side of Røldal on the old road, towards Odda is slow but worth the effort. The rest of the main road to Odda was quiet enough when we were on it, although care is needed near Låtefoss because of tourist traffic near the falls. After Odda we recommend taking the road along the western side of the fjord because the ferry at the top of it, from Utne, is much more frequent than the ferry from Kinsarvik on the eastern side of the fjord. However the eastern side of the fjord is lovely in the evening sun, there are plenty of stalls selling cherries at the side of the road. You have to do is make sure you get to the ferry from Kinsarvik on time the following day.
The route up to Førde then takes you over several notable climbs, a short one at Granvin, then a long one over Vikafjellet after Voss (harder in this direction than the other way). We had a rest day before tackling the next climb up over Gaularfjellet and later in that day before Førde there is a shorter but steep climb. From Førde we left Route 3 and had one big climb after Naustdal on the way to Florø. According to signs next to the road it is closed at the top where it passes through a short tunnel. In 2008 this was open for all traffic and in reasonable condition. The rest of the route out to the coast is undulating and more demanding than you'd expect.