Full-text index in partitioned table
I did some more research and found a couple of useful articles with best practices regarding table partitioning and full-text searching on large tables. As I haven't received any answers to this question, I thought I'd post what I've found here for future reference.

I'm still reading those, but for what I've already read, I've found both of them useful and relevant to this particular situation:

SQL Server 2005 Full-Text Queries on Large Catalogs: Lessons Learned:


  The observations in this paper are based on tests run in the SQL
  Server Customer Lab for a customer who needed to scale up full-text
  search to a much greater potential volume. The paper describes the
  customer scenario, provides an overview of SQL Server 2005 full-text
  concepts that bear on the results, and offers lessons learned and
  recommendations for using full-text queries on large catalogs.


Partitioned Tables and Indexes in SQL Server 2005


  Summary: Table-based partitioning features in SQL Server 2005 provide
  flexibility and performance to simplify the creation and maintenance
  of partitioned tables. Trace the progression of capabilities from
  logically and manually partitioning tables to the latest partitioning
  features, and find out why, when, and how to design, implement, and
  maintain partitioned tables using SQL Server 2005. (41 printed pages)