With the 1.5 update I had a LOT of times huge fps drops when going from in- to outdoor scenes. Also again the CTDs were back a lot with the 1.5 update.
The "Unofficial Skyrim Patch v1.02 BETA" mod did hugely improve that. Also less CTDs now. It does not fix other 1.5 bugs like the weird shadow lines, no AO and so on.
For those with same issues, see here for info: http://www.gamesas.com/topic/1359350-beta-unofficial-skyrim-patch-thread-3/