I've been using vga_switcheroo for a while now with a lot of problems. I've got a Lenovo U330 with Radeon 3450 and Intel 4500MHD and:
1. LVDS doesn't come back after suspend when using radeon.
2. Intel freezes Xorg when switching both_cards > integrated_only. I have to do both_cards > discrete_only > integrated_only.
3. When switching to integrated card with HDMI (attached only to Radeon) connected, kslowd000 starts using 100% CPU.
4. While using Radeon, I can only suspend once. Suspending more than once causes the Xorg to crash.
I've reported the bugs a _LONG_ time ago. With no response
I'm really thinking about switching back to using lenovo_acpi http://github.com/doudou/lenovo_acpi because I'm just starting getting fed up with this.