What is the terrain like? Is it mostly countryside or do you go through a lot of towns/cities? Paved or gravel roads or country paths?
The terrain is very mixed. A lot of walking on minor roads with one very long section - over 30km - at the side of a major surfaced road. A number of sections through pine forest including one stretch of about 40km without significant towns or villages. No very high mountain sections although the crossing from Sweden into Norway is a long isolated stage through significant hills. For an experienced walker none of the stages presents any technical challenges. The route passes through small towns or villages on most days but few large towns.
How much time did you need to do the whole thing? Did you have to plan your day based on where you could find a place to stay?
I carried a small tent and camped most nights. Swedish and Norwegian law and culture are very open to wild camping. Partly for convenience as I was not limited in my stages. Partly to reduce cost. And partly because I walked in May when many of the accommodation options were closed. I walked the route in 17 days which most people would find very fast - but with temperatures often close to or below freezing and with nowhere sheltered to stop on many days there was an incentive to keep moving
Did you need a sleeping bag? We're going in late June/early July (just firming up the dates) but it still seems like it is pretty cool at night?
As I mentioned I walked in May and was occasionally camping in temperatures down to -5C. I carried a warm sleeping bag and winter clothing. Even in June I would go prepared for cool nights and personally I would always carry a sleeping bag. If you enter the names of some of the towns along the route into the
www.weatherspark.com website search box you will find average weather figures for the route which should give you a good guide.
Did you have to carry your own food or were there lots of places to eat?
I carried at least one full day's supply of food at all times. There were several stages where no food was available for 24 hours or more and when I expected these I would stock up with at least two day's supply. Walking in summer you will find more places open but there will still be stages where carrying food will be essential. This is one of the ways in which the route is VERY different from the
Camino Frances. Planning and preparation are essential.
Were there albergues or hostels for pilgrims, as in Spain, etc or what kind of accommodation was there along the route?
There are some pilgrim hostels and other (relatively) low cost options along the route but again nothing like the
Camino Frances. Accommodation is much further apart and generally considerably more expensive than in Spain. Unless you are prepared to camp you may find yourself spending more time in private B&B type accommodation which is often expensive in Sweden and even more so in Norway. The ST Olavsleden website provides details of accommodation. As the route grows more popular the range of accommodation has grown - even in the 18 months since I walked it.
http://www.stolavsleden.com/accommodation-services/