My Cox Surestarts start by hand with only a few flips, run very well, and are consistant runners. Plenty of power for anything under 14 oz or so. I have one on a sport Pylon racer that has well over 50 flights of about 5 to 6 minutes each and still runs strong. I've probably burned 2 quarts of fuel through this one engine.
If you can't get a Surestart to run you will have no better luck with a Norvel. Stick to electrics. Norvel engines are a different class of engine for a little heavier airplane and have their own unique "way about them" just as the Cox engines do.
Practically all of the bad memories some have with Cox engines are related to engines with tanks. The Surestart is a different breed without the troublesome tank.
The only problem that I can see with the Surestart is the lack of a throttle.