I passed the magic 10000 mark just before my UK vacation for my granny's 100th birthday party.
My only observation is that I am starting to see more issues with errors in cross-linking of tracks in the indexing system on the iPod. Occasionally, one or more tracks on an album will turn out to be from a completely different artist and album. This can be corrected by re-loading from the last backup, but it is annoying. When you are trying to listen to Stephen Stills and find a Terje Rypdal tune instead, it jolts you...