Perhaps, the latest version is even slower? I think OOo doesn't work on slow Java framework ported for C. 
I'm going to give you some advices which can help to optimize OpenOffice.
1. Fonts.
It was one of the biggest problem with starting GIMP 2.2x. In 2.4x releases it creates cache file. I think OpenOffice has implemented font caching (if needed) and looks for new fonts very fast.
2. Optimization guides.
I like to make even micro-optimizatons in PHP. You can find much information about PHP scripts optimization. I believe that there are lots of articles about optimizing applications in C. Smile
3. RAM operations are viele much faster than disc operations.
4. Do not make so many copies of variables and not needed variables which can increase RAM usage.
5. Maybe some functions aren't always needed and should be loaded e.g. only with Calc, not Writer... or only in Impress, not in Calc, etc.?
6. Maybe operating systems provide faster functios of some actions (e.g. looking for files, disk operations) or OpenOffice can implement faster functions than in OS?
I believe optimizing it is possible. However, the responsibility time of OOo should be fixed too.
PS. "TOC and indexes" tool loads very long too...
