First, Gluonpilot is a single-board, open source IMU-based autopilot created by Tom Pycke in Belgium. Tom is a long-time autopilot designer and one of the best in the business, so this is solid gear. It's available for $322 with GPS from his store.
The hardware is a nicely-designed two-sided board, a little wider than APM but shorter. It uses a fast dsPIC processor, and supports six RC channels in and five channels out (with the option of driving two aileron servos). It has 1 MB dataflash onboard, and a pressure sensor (no magnetometer). It uses a FTDI cable for programming and communications with a desktop setup utility.
When you first get the board, it comes with cables to connect 4 RC channels, which is a little confusing because you need the 5th channel to control the autopilot. After a little digging around on the wiki, I figured out that you need to solder on two more pins to some spare holes and find some jumper cables to connect the 5th (and optionally 6th) channels.
The code is pre-loaded, so you just need to connect the included FTDI cable to the board (make sure the black cable is closest to the edge) and plug it into your PC. If you're using Windows Vista or 7, the FTDI drivers will be automatically loaded. The Gluonpilot instructions say the board can be powered by the FTDI cable, but I found that wasn't the case with servos connected. It shut down my USB hub like that, so I had to power the board with an ESC while using it on the bench.
Once you've got it plugged in, you can start the configuration software (Windows only). There you can set up your RC, check the sensors, download datalogging files, and do some mission planning. Overall, it's a very nice and simple setup process, similar to the ArduCopter Configurator. Everything is handled by one app, and once you've got your FTDI working, communications is fast and easy. Changes are written to the board via this app, and you can even update your firmware with it. No need to mess around with code.
Here's the RC setup screen:
I found the RC setup a little confusing. It turns out that the servo output 1 and 2 are both for ailerons (I guess for people who use two aileron servos without a Y connector?), so for regular configurations, you actually have to skip Output 2 and put the elevator on Output 3. I eventually figured that out by re-reading the manual, so no biggie.
You can also see the sensors working in this screen:
The configuration also has a very simple Ground Station that looks like this (you can also use it to open Google Earth and see a moving map)
But the good news is that the terrific Happy Killmore GCS also supports Gluonpilot, so I'd suggest you use that instead.
Unfortunately, there is no dedicated port for an Xbee for wireless telemetry, so you'll have to plug wires onto the FTDI port and unplug them when you want to change Gluonpilot configurations or change your mission. That means you'll need to put the autopilot in a place in your plane where you can get easy access to it and deal with some fiddly wire swapping at the field. I hope in the next version of Gluonpilot, Tom adds a dedicated Xbee connector (although I'm not sure if the dsPIC he's using has a spare serial port for this).
Mission planning is done via a scripting language. The configuration utility lets you enter commands pretty easily, but there is so far no point-and-click waypoint entry as you can find in most other autopilots, so it's a bit of a hassle to look up lat/lon on Google Maps and copy them over. So right now Gluonpilot is better for relative waypoint (go 100m north of current position). Here are the available commands:
I haven't had a chance to fly Gluonpilot yet, but by all reports it's very solid. Now that it's supported by the HappyKillmore GCS, it has a proper Ground Control Station. The only other big missing software piece is a point-and-click Mission Planner. Otherwise, it seem to be in very good shape and quite mature for a one-man operation (no surprise if you know the inimitable Tom!)
Tom has flown a quadcopter with Gluonpilot, but given that it doesn't have a magnetometer or any way to add one that I can find, that doesn't seem like the best fit for this board. Instead, it seems perfect for fixed wing aircraft, especially those with easy-to-access cockpits where you can plug in the FTDI cable and swap wires to add the Xbee.
Tom is also planning to add an on-screen-display (OSD) interface with a daughterboard, so that will be cool to see.
Overall, this seems like a very good launch from a top autopilot designer. It's somewhat similar to the UAVDevBoard (similar processor) but is easier to set up and the hardware is more sophisticated, with a built-in pressure sensor and datalogging (although it doesn't have as strong of a community yet, and it costs twice as much). Overall, at this point I'd recommend this for people who want an easy-to-use autopilot for fixed-wing aircraft and don't mind not being able to click on a map to enter waypoints.
Next, I need to fly it and see it it works as well in the air!