There is a use case where Steam causes heavy flickering when you open the dash. The whole screen turns grey and starts to flicker.

How to reproduce:

1. Open Steam and optionally a Steam chat (with a chat window opened the flickering is always there, with only Steam opened it doesn't happen often)
2. Move to another workspace or move Steam with the chat window to another workspace
3. Now open the Unity dash in your workspace.

System info:
Processor Information:
Vendor: GenuineIntel
Speed: 2534 Mhz
4 logical processors
3 physical processors
HyperThreading: Supported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Supported
SSE4a: Unsupported
SSE41: Supported
SSE42: Supported

Network Information:
Network Speed:

Operating System Version:
Ubuntu 12.10 (64 bit)
Kernel Name: Linux
Kernel Version: 3.5.0-21-generic
X Server vendor: The X.Org Foundation
X Server release: 11300000

Video Card:
Driver: NVIDIA Corporation GeForce GT 540M/PCIe/SSE2

Driver Version:  4.3.0 NVIDIA 313.09
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID:  0x10de
DeviceID:  0xdf4
Number of Monitors:  1
Number of Logical Video Cards:  1
Primary Display Resolution:  1366 x 768
Desktop Resolution: 1366 x 768
Primary Display Size: 13,54" x 7,60"  (15,51" diag)
                                        34,4cm x 19,3cm  (39,4cm diag)
Primary Bus: PCI Express 16x
Primary VRAM: 1024 MB
Supported MSAA Modes:  2x 4x 8x 16x 

Sound card:
Audio device: Realtek ALC272X

Memory:
RAM: 3819 Mb

Miscellaneous:
UI Language: English
LANG: de_DE.UTF-8
Microphone: Not set
Total Hard Disk Space Available: 552038 Mb
Largest Free Hard Disk Block: 423290 Mb