First of all I think that the SS CMS is the easiest to install and use. I've tried every other CMS and they are cluttered and clunky but not slow. I have not found one I like, only SS.
Having looked around this forum I have to say that the most disappointing aspect of SS is the very slow performance. It would appear that as the site grows, the site slows. My site is in development as I write. There are only 11 pages, and many more to come, but the performance is terrible.
It's now 7pm UK time and my new page with nothing on it is taking 11 seconds to load. Once that page has loaded and I request any other page it's exactly the same. There's no way anyone will wait that long for a site to load. The back end is also dreadfully slow. My grandmother is quicker!
What I have also noticed is that since I have installed this on one of my UK based servers which is hosted at UK2.net, I am having issues with exceptionally slow server performance. I can check this in my WHM server status menus and the CPU load is over 30% and being flagged in red and memory usage has rocketed past 40%. Normally those figures are server load 6 - 15%, memory around 12 - 20%. I have had this server for over 12 months and NEVER had any issues at all. I have over 50 sites currently on this server, mostly e-commerce sites, and they were exceptionally quick. They have certainly slowed down since SS was installed. I have raised tickets with UK2.net and they have stated there are no issues. I believe them.
I have also loaded SS CMS on my other server which is hosted by a completely different company, Hosting Unlimited, and the performance on that is exactly the same.
As much as I had thought I had found the 'perfect' CMS I sadly have to state quite the opposite. It's grossly slow.
Well, for me it's back to the drawing board and SS will be binned. I can only say that I have spent 2 weeks with it but unfortunately with it's crap speed issues it's a non starter.