I, too, am having some severe framerate issues in the dungeon, on an Intel-integrated-video laptop (dxdiag below).
With the default configuration, in full-screen mode: In the shop, I'm getting a pretty consistent 35-40 fps. Outside the shop (menus; elsewhere around town) I'm getting a rock-solid 60 fps. In the Hall of Trials, I get a meager 5 fps. Two things are interesting about this, though:
1) Checking the lower three dungeon performance settings (simple models, no light processing, no fog) gets me up to about 30 fps in the Hall of Trials, and if I happen to find a long corridor that leads far away (three sections?) from any rooms, it jumps up to 60 fps
2) I have no framerate issues with Jade Way. I can uncheck all of the dungeon performance settings and set the frame limiter to 60, and it happily gives me a solid 60 fps. And yes, this strange performance divergence between the Hall of Trials and Jade Way is very repeatable.
I updated my video driver today hoping it would help, but alas.
Other than this, I'm having a lot of fun with the demo!
<dxdiag>
------------------
System Information
------------------
Time of this report: 8/28/2010, 22:41:03
Machine name: [redacted]
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_gdr.100427-1636)
Language: English (Regional Setting: English)
System Manufacturer: LENOVO
System Model: 1951WPX
BIOS: Phoenix FirstBIOS(tm) Notebook Pro Version 2.0 for ThinkPad
Processor: Intel(R) Core(TM) Duo CPU T2500 @ 2.00GHz (2 CPUs)
Memory: 2038MB RAM
Page File: 921MB used, 3010MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.5512 32bit Unicode
---------------
Display Devices
---------------
Card name: Mobile Intel(R) 945 Express Chipset Family
Manufacturer: Intel Corporation
Chip type: Intel(R) GMA 950
DAC type: Internal
Device Key: Enum\PCI\VEN_8086&DEV_27A2&SUBSYS_201A17AA&REV_03
Display Memory: 224.0 MB
Current Mode: 1024 x 768 (32 bit) (60Hz)
Monitor: Default Monitor
Monitor Max Res:
Driver Name: igxprd32.dll
Driver Version: 6.14.0010.4926 (English)
DDI Version: 9 (or higher)
Driver Attributes: Final Retail
Driver Date/Size: 2/15/2008 13:12:06, 57344 bytes
</dxdiag>