I have worked with many clients converting legacy files to InDesign 2.0 and CS. Overall, the experience has been fairly positive as long as the client sets her expectations appropriately. It is extremely important for you to understand that InDesign uses its own unique composition engine to flow text.
For this reason, the most prevalent challenge you will have is text reflow. So, for your longer documents, there is greater potential for text reflow. You therefore need to pay close attention to line breaks and wraps. As mentioned earlier, the Paragraph Composer controls found in the Paragraph palette can be employed to affect changes and improvements to the text flow.
Having said this, I can’t imagine that this issue is more challenging or time-consuming than recreating your entire file. I have worked with page layout applications since the late 1980s (think Ventura Publisher) and have never been more excited by a product that delivers so many features and options that meet the demands of the marketing/ communications professional.
You will appreciate its robust typographical controls, rich creative tools and features, tight integration with the rest of the creative suite, long document publishing options, and cross-media and interactive features that allow for the repurposing of content. In the vernacular, it’s the total package.