Sgt_Kickaxe - 4:14 am on Jul 21, 2011 (gmt 0)
I would have said yes until I saw the announcement about on-demand indexing for Google CSE data recently made over at code.google.com.
I saw that too but it only impacts results displayed on your site, not in Google's index. The two are not different for very long so the resources required may not be worth the benefit.
The added functionality of adding an expires tag to urls in your sitemap is great but again I'd probably upload a sitemap for the purpose of removing something on an as-needed basis.
Still no sign of any rankings loss btw. Slightly increased crawl rate but not out of the norm so it's likely not attributable to the sitemap removal.