Personally, I think ID CS4 is worth the upgrade for anyone who uses ID regularly. It'll be about 18 months before the CS5 comes out, so if it'll save more than $10 worth of time a month, or about 50 cents a working day, it's worth it.
Let's hope Adobe adds another 'smart' to CS5--Smart Flows in conjunction with Named Text Flows.
Named Text Flows would let users assign a name to a text flow, so ID would know which text frames go together. That means no more fiddling with confusing blue lines. Smart Flows would then automatically assign the flow order based on rules like front to back and top to bottom. Move a frame, and its place in the flow would automatically change. Need to link text on page 20 with a continuation on page 87, as in magazines and newspapers? Easy, just assign them the same named text flow. Automating "Continued on page 87" would also be easy.
You mentioned Adobe's mistake in making text shadows and highlighting a frame feature rather than a text or paragraph one. They made the same mistake with columns. ID should let users make the number of columns a paragraph feature, so text can flow from single-column heading to multi-column text simply by setting paragraph styles. As things stand now, that's the #1 missing feature in ID. Seriously powerful sidebars would also be helpful.
