I ran merges using Pagemaker 7. Setting up the merge was a little tricky at first, but only because the instructions were a tad ambiguous, to put it mildly. But once I ran a couple, I enjoyed running merges in Pagemaker because it offered design advantages.
I am now using InDesign CS—not yet CS2 or CS3—but CS does not offer a merge capability. I could have purchased the Pagemaker Data Pack which would have added the merge function, but I drifted away from having to run merges. InDesign CS2 and CS3, however, have the merge function included. I took a quick look and it appears that the merge function in InDesign CS2 and CS3 is similar to what it was in Pagemaker. So my message is that you can run merges in InDesign, current version CS3, to create a series of Christmas cards and birthday cards. If I had to run a job like yours, I would use InDesign CS3.
One word of caution. I’m running InDesign CS on OS 10.4.11 (Tiger) and I haven’t run into any problems. I don’t know how CS3 runs on Tiger. CS3 and Leopard, however, produce a few glitches according to users. Since merges are your business, I would contact Adobe and ask if the merge function in CS3 runs smoothly on Tiger or Leopard, whichever OS you’re using.
Very briefly: when running merges in Pagemaker (and it looks the same in InDesign), I placed the graphic or graphics common to all the pages on the master page. Then I formatted the page that would recur, sometimes a single letter size page, sometimes a four-, six- or eight-up page. The data had to be in csv format, usually from excel. Whenever the graphics on the master page changed, I had to run another merge. For example, if I were sending out 1,000 Christmas cards using one graphic and 1000 cards using a second graphic, I would have to run two different merges containing 1000 cards each. I never had to run a job where the merge placed a different graphic on each page, much like placing a different name, address or text on each page. I think it can be done, but the merged document would be huge.
I successfully avoided Publisher all these years until about six months ago. I’m doing some work for an organization that is equipped with Windows XP and owns no software other than what comes with Office 2003. I have to create documents in Publisher so that the organization can make edits down the line. While Publisher may be serviceable when creating a simple document, it lacks many features that I rely on in InDesign (and lacks features that I relied on in Pagemaker). I would urge not to let your experience with Pagemaker deter you from exploring InDesign.
One comment about your experience with Pagemaker and books. I avoided creating large documents in Pagemaker. Instead, I used Pagemaker to create chapters or sections—that is, smaller parts—then compiled the end document, sometimes quite large, over 1000 pages, in a pdf. This might not allow sufficient flexibility for high end production. But a pdf was more stable than a Pagemaker document, and printers I used were happy to work from a pdf document.