CMS can make or break your seo campaign. It can break, if it doesn't allow you to customize the title tags, meta description, URLs, anchor text etc. If it duplicates its own contents, create duplicate title tags, doesn't allow you to apply 301 and host dozens of other negative factors which act as impediments to rankings.
On the other hand, a CMS is just a canvas for art. It doesn't have to get in the way of the idea you want to represent. If the niche/content of your site bears substance and makes people want to visit or link to it, then you won't be experiencing much of a problem, regardless of your CMS.
Google has recently said speed is a consideration, but not to be concerned with it unless your site/server performance was abysmal. I believe that as more and more bandwidth and resources are coming available, that you run out of excuses for slow/poor performance and it will be considered more and more over time. Google (on behalf of the user) wants everything fast. With cloud and grid options available, there's really no reason to have a slow site anymore. If your pages frequently take a long time to load, Google is absolutely correct to consider it in the rankings. If I click on a search result to a site and it hasn't loaded after say 10 seconds... I click the back button and look for the next result (or try to load Google’s cached version of the page).
Please wait...
