My SOP was 1000-1100 words, maybe a little shorter for a school with a stricter page count. For what very little it's worth, I got some really, really positive feedback on it at interviews and from current grad students and mentors I had look over the generic draft. It was pretty much entirely research-focused and very straight forward, tracing the progression of my research interests and experience as they evolved and then connecting that to the program/school psych in general, and the work of my POIs. I closed with a very brief statement on how the program would be a good fit for my professional goals. IMHO, it's important to tell a story with your SOP, not just talk about your experience. I focused on a few key projects that were most relevant to the work I was applying to do and left out the stuff that wasn't as relevant (it was still on my CV, of course, so I wasn't hiding it or leaving it out entirely) to the "story" of why of I was applying to that particular program/POI.
Also, if you are really struggling with a particular SOP, think about whether you really want to apply to that program. One of the schools I applied to last year very explicitly wanted a SOP about clinical experience, teaching experience, and coursework, with the research experience a pretty obvious and fairly distant second. I really struggled with writing that SOP because my background was very research heavy and research was largely how I formed my research/clinical/professional interests. In retrospect, that should have tipped me off that perhaps the program wasn't a great fit for me. It was also one of the programs where I didn't get an interview invite, FWIW.
