They are totally different from AVR family but I could give it a try for an ultra fast motion controller with 4 or more axis. In the next link this one even has 3.2 inch touch LCD screen among other connectivity addons:
Open107V ARM Cortex-M3 USB STM32F107VCT6 MCU Development Board Kit
And a cheap programmer/debugging interface for it:
J-Link V8 ARM USB-JTAG Adapter Emulator - Black

So if anyone is open for donation for one of these please let me * It could really change everything we thought about motion simulator electronics.
Best Regards,
Thanos
EDIT: Here are some specifications of this microcontroller:
STM32F107VCT6: ARM Cortex-M3 32-bit RISC
- Operating frequency: 72MHz, 1.25 DMIPS/MHz
- I/Os: 80
- Memories: 256K Flash, 64K RAM
- Communication Interfaces: 3 x SPI, 3 x USART, 2 x UART, 2 x I2S, 2 x I2C, 1 x Ethernet MAC, 1 x USB OTG, 2 x CAN
- AD & DA converters: 2 x AD (12-bit, 1us, shares 16 channels); 2 x DA (12-bit)
How to donate for this development board:
If you like to donate for this purpose please go to my blog and click on the paypal donation button on the top right side of the page:
http://motionsim.blogspot.com/

I have no other way of placing donation button for it here as paypal requires special html code for link protection.
If donations for this development board doesn't reach its target within two months, I'll reverse all donations about it.
Keep in mind that donations are subject to 4.6% fees going to paypal for the service (for example: from $10 donation, I get only $9.54)
List of the participant names can be place here (unless instructed otherwise) along with the percent of collected funds toward target.
Thanks
Project donation target: $97
Donation amount so far: $150
List of donors:
- Terry F. (telfel)
- David L. (motiondave)
- Richard D. (riton)
- Jakub V. (mambo)
- Gilles C. (vicpopo)
- John T. (John)
- Mirco L. (yokoyoko)
The Open107v Motion Controller Project thread is now can be found here: http://www.x-sim.de/forum/viewtopic.php?f=39&t=359