I have been playing the game on 1920x1080, all detail settings maxed except water refracting/resampling reduced and so far, I've only experienced very minor glitches after playing about 90 hrs during my first playthrough. FPS has been around 40-50 in most areas.

However, today I noticed that there is one spot in Vault 11 where the game keeps crashing to desktop.

on the lowest level when entering the Reactor room, there are two giant mantises inside and when they lunge toward me, the game crashes. I tried reducing the overclock and it is still happening.

Is this common? should I reduce some kind of video setting in order to get through vault 11?

SPECS:
Envy 15, AMD Radeon Mobility 5830, i7-820qm, 16GB RAM, dual Intel X-18M G2 SSD in Raid0 (160GB x 2)

Also, using the 4GB exe loader and the replaced d3d9.dll

Do you have any companions following you? If so, have em "wait here" at the entrance while you explore the vault, particularly the reactor room where you are encountering the crash.
The latest patch may have addressed some companion issues, however I've encountered plenty since latest 1.2 patch and as a result, I have managed to avoid most crashes by always having companions wait behind while I explore any indoor areas.
Vault 34 is the only location this workaround has not been successful for me.
Good luck

I didn't ever have any companions with me in Vault 11. I had two active companions, but they were waiting at their original location where they were first encountered (ED-E in Primm and Boone in Novac).

After some experimenting, it seems the game only crashes at this point if I'm using melee weapons. Perhaps it has something to do with the super slam perk knocking the mantis backwards before the mantis leaps forward to attack? overclocking or using default clocks doesn't have any effect, however, switching to ranged weapons before approaching the mantis in the tunnel prevents the game from crashing.

This crashing doesn't seem to occur with mantises in any other location, only on the bottom floor of vault 11 just before entering the reactor area.