I remember the terrors of Fallout 3 modding where adding non-persistent content to exterior cells could potentially contribute to unpredictable crash on save errors for some people. The solution seemed to be either make every external cell object persistent (chewing up memory), converting the.esp into an .esm, or running FO3 master update.
Any word on the situation with New Vegas modding? Is it still safer to bite the bullet and convert the .esp to .esm, or is non-persistent external cell content "safe" now?