This summer will be the third time we have flown with them.
1 was Minneapolis to Copenhagen, Helsinki to Minneapolis 2008
2 was Minneapolis to Paris round trip 2009
3 will be Minneapolis to Amsterdam, Munich to Minneapolis 2010
Their planes are the smaller, single aisle, 3+3 style, but I don't see how that makes any difference. It was clean and modern. Coach is coach. 2008 had seat-back tv shows & meals. 2009 had movies and no meals (cost cutting). The layover in Iceland is painless - an hour or less in a small, pleasant terminal with shops. Basically, you switch planes, get up and stretch your legs, pee, glance at the terrain of Iceland near the airport (interesting) and move on.
If you have an interest in seeing Iceland and/or Reykjavik, you can arrange a painless layover for no added cost. We did a 24-hour layover in 2008 and wished it were longer, but we were glad we did.
Flying open-jaw in Europe is simple and economical. Depending on the combination of cities, you can even wind up saving a little compared to a round-trip ticket. Use their web site and search multi-city for different options. Here's a hint; do some RT flight searches first. These display a 2-week window of fares and sometimes show days that flights are cheaper for one leg of the trip. Do this with multiple cities and keep track of those sale legs. Then put together a multi-city search using dates that were on sale both directions and you can sometimes find some good deals if your schedule is flexible.
Another asset for parents with children under 12 is that they offer small discounts for children (about 15%) while most airlines don't.
A few of their Europe destinations are summer only and not every day. Others have 1-2 flights per day.
They service most common destinations in northern Europe, but not the south or east. For Prague, Vienna, Rome, Madrid, Lisbon, etc. you will have to fly some other airline.
But I have nothing but good things to say about them.