Titles work really well in iMovie '08. Previous versions of iMovie had to render titles when you added them, taking a lot more time than the instant placement you get in '08. But there is more to iMovie '08 titles than just the speed.

Moving titles
First, you can place titles wherever you want in your movie with pinpoint accuracy. Once a title has been placed in your movie--represented by a blue flag running above your clip, you can drag that title to any point in the movie. This is even true of titles "over black". In iMovie HD, you'd have to split a clip at the point you wanted a title to enter, then add the title to the second half of the split clip.

Lengthening titles
Another really nice feature of '08 is the ability to lengthen or shorten a title quickly. Simply grab the end of a blue title flag by clicking on the end with your mouse and drag the title to lengthen or shorten it. In iMovie HD, you'd have to select the rendered title footage and readjust and rerender the title, guessing at the right length with each render. This new way is much faster and easier.

Spanning titles
By either moving a title or lengthening a title, you can get a title to stretch across multiple clips. In the case of lengthening, you'll notice that you can drag the end so it runs across as many clips as you like, with no rendering! (You just can't span a title across another title.) Very handy and much faster and more accurate than iMovie HD.