I maintain a list of
cheap FPGA development boards that you might be interested in. The Atlys isn't exactly cheap (and thus isn't actually on the list), but it's definitely the most capable board in its price class and I'd highly recommend it if you can afford it or want to work with digital video. You can easily add VGA output to most FPGA boards or microcontrollers using a connector and some resistors, but DVI/HDMI input and output requires some careful PCB design, especially at higher resolutions.
and JTAG devices like this can be connected in paralel so that you can program another board from teh built in JTAG programmer on the Atlys
I'm not 100% sure that this would work because the JTAG connector and the USB programmer are connected in parallel rather than chained, but I could be wrong. If you really need a Xilinx JTAG programmer, I'd get one of the (relatively cheap) USB Platform Cable clones from eBay.
reliably interfacing with the device, on the other hand, will prove to be a non-trivial endeavor. Compared to the Nexys2 or 3, the Atlys doesn't look to be as convenient for interfacing external devices...and they milk the marketing cow for all its worth too: 48 I/O’s routed to expansion connectors translates to a whooping 8 GPIO + 20 differential pairs on a VHDCI connector
The length-matched, impedance controlled differential pairs are actually the thing I like best about this board! Don't forget that you can use 20 pairs as 40 single-ended I/Os, or a combination of single ended and differential.
The VHDCI connector was a little bit problematic when the Atlys was first released, but now Digilent sell the appropriate mating connector, and there are a few other alternatives. I've listed some of them on my
Digilent Atlys resources page. You should be able to get one of the connectors as a free sample, and then make up a small breakout board with 0.1" headers for next to nothing. Hmm, would anyone be interested in something like this if I were to sell them?
Furthermore, advertising 500MHz+ clock speeds is suggestively full of crap and misleading.
Yeah, it's not quite clear what they're advertising here. The on-chip PLL will generate frequencies as high as 1080 MHz, though you can't run the FPGA fabric at these speeds. SERDES can easily be used to input and output serial data streams at well over 500 MHz, perhaps even at just over 1 GHz, however the speed grade of the FPGA on the Atlys remains a mystery.