I've got a new Dell laptop with a mobility 3450 which seems to work reasonably well with latest Ubuntu and fglrx. I also tried radeonhd which also appeared to work. I doubt there's a whole lot of difference in support between the 3450 and 3470.
Mind you, I'm not a compiz user and haven't really had chance to try out video on it...but you can certainly run gnome.
Have you tried and failed, or are you just trying to find out if it is likely to work before you give it a go?
This sounds like missing device IDs. Sometimes IDs are used on a product and we don't get told about them either. For anyone whose GPU is not being recognized, please run lspci and let us know what the PCI IDs are for your GPU.
My hd3470 on a toshiba a300 laptop has been working fine too since catalyst 8.11 I think, although it is recognized as a generic hd3400 series card and I cannot get temperature readings (I posted another topic about that). Haven't tried radeon/radeonhd since I need power management (read: battery time) badly on this laptop (not that I'm sure it is even working with fglrx, but at least I can try to activate the option on ccc )
lspci -v reads
01:00.0 VGA compatible controller: ATI Technologies Inc Mobility Radeon HD 3400 Series (prog-if 00 [VGA controller])
Subsystem: Toshiba America Info Systems Device ff50
Flags: bus master, fast devsel, latency 0, IRQ 16
Memory at d0000000 (64-bit, prefetchable) [size=256M]
Memory at f0200000 (64-bit, non-prefetchable) [size=64K]
I/O ports at 2000 [size=256]
[virtual] Expansion ROM at f0220000 [disabled] [size=128K]
Capabilities:  Power Management version 3
Capabilities:  Express Legacy Endpoint, MSI 00
Capabilities: [a0] MSI: Mask- 64bit+ Count=1/1 Enable-
Capabilities:  Vendor Specific Information <?>
Kernel driver in use: fglrx_pci
Kernel modules: fglrx