In fact I met nearly every issue mentioned in the jUpgrade forum, see http://redcomponent.com/forum/92-jupgrade, but thanks to the answers provided in the forum, I have been able to overcome them all.
A "jUpgrade for Dummies" guide would be very useful. But I guess volunteers are needed here :-)
Thank you very much for this very helpful extension. It is very, very useful. It is clear that many people are frustrated by the amount of work needed during migration, -it took me 3 evenings, ie about 10 hours, to complete migration- but I guess this cannot be avoided if you have a customized web site.
The most important item that helped me was to remove everything specific (specific modules or plugins) that I use on top of Joomla 1.5 before migrating. I have re-installed them afterwards.