This has been bugging me since I started using WP in 2006. When you hit the "save" or "update" button after writing a post or editing a theme file, the cursor moves to the top of the Edit window, and the whole page being displayed also reverts to the top-of-page position.
For long posts, this is just maddening. Also, given how uncompact the default WP admin layout is, update buttons and the like often require scrolling to reach. To have to re-scroll back to the same position on the page, and the same position in the Edit box, gets r.e.a.l.l.y O.L.D.
It can't be that hard to retain positions in a buffer somewhere. Please do it!