I came from SME and don’t regret the change!
I wouldn’t say that NS is a good “upgrade” of SME. The only thing they have in common anymore is the e-smith templating.
SME is a good an stable server, but here the community is so great.
You won’t have to wait long for help or any replay else.
NS is easier to handle IMO, more modern, more active in development and more innovative.
So it’s a good idea to change from SME to NS for many resons.
But maybe I’m a liitle bit biased to. 
I am doing a lot of testing last few days.
Fired up some new VM’s of NS7.4. Installed webtop5 on one and on the other the printserver module with SavaPage. The latter to recheck if the howto is fail/fool proof. And yeah, it works perfectly!
well… no doubt this community is great but…
I can frankly say that you haven’t to wait too long for a reply on SME’s forums, since I read all the posts there and I answer in minutes (I’m Stefano there, you can easily check ;-))
Fair enough 