I purchased a Garmin Edge 800  over the holidays. As an avid 705 user, I was excited to see what the 800 was all about. Overall, it is a solid unit and will stay on my race bike. For many 705 users, though, I don't think the upgrade is worthwhile.
The Edge 800 is a top-end GPS equipped bicycle computer. My Edge 800 shows 1051 miles of use over the course of 65 hours in a month since purchase (Menu > History > Totals). In that time, I've become more familiar with the unit. My overall impression is that it is more pleasant to use than the 705, but not always more functional. I've noted some highs and lows, as follows.
- Vastly easier to calibrate a power meter.
- Larger screen, lighter weight (110 grams to 97 grams), very slightly wider and shorter.
- Vastly improved mounting system, using quarter turn lock (same as Edge 500).
- Touchscreen may be more durable. My Edge 705 has cracked seals on the buttons due to years of use. Some have joysticks that fail, too.
- Much faster processor: faster routing, faster power on time, usable map screen!
- Actually usable with topographic maps, like Garmin US Topo 24k
- Temperature support.
- Vertical speed field.
- Up to 10 data fields per page, up from 8.
- 3 data pages, up from 2.
- USB port is at bottom of unit - sits flat on desk
- Much easier to type thanks to touch screen.
- Unit is more streamlined and less likely to snag in a bag due to lack of touch stick.
- Ability to save workout files directly to external storage device.
- Able to copy custom workouts from 705 easily.
- Activities stored in more efficient .fit format - no need to regularly purge and compress bloated .tcx, faster uploads.
- Files are named according to local time zone setting, not UTC.
- "startup.txt" file allows me to put my name and phone number in while powering on the device in case it gets lost.
- Possible dealbreaker: No way to route using .GPX files. They all appear as courses, not routes. See https://forums.garmin.com/showthread.php?t=14186&page=3 .
- Screen is really hard to read in daylight due to reflective finish. Backlight helps, but unit drains battery really quickly with the backlight on high.
- On the power meter screen, the "Calibrate" and "Rescan" buttons are right next to one another. If you have fat fingers and hit the wrong one at the start line, well, no race data for you.
- No file transfer feature. With the 705 I could wirelessly send routes to other users. Not so anymore.
- Software automatically goes in "bicycle" mode when calculating a route. If I have a .TCX route that intentionally routes me on an Interstate (i.e. in places where the Interstate is the only possible route), bad things happen. What if I actually want the GPS to calculate a route using the car/motorcycle preference? I need to change the routing mode manually, every time.
- Still only reports as a USB 1.1 device with slow transfer speeds. There is absolutely no need for this. I have to pull the SD card to transfer map files, lest it take an entire day.
- Workflow is partially designed around Training Center, which is not good for Linux users. Uncompressed XML is bad for ride data but really good for creating content.
- Not compatible with .TCX courses or workouts. Requires an additional step through Training Center.
- No workouts included. I ported some from my 705.
- Garmin logo when viewed from the front is huge!
- Less internal memory: 128 MB (105 MB available) instead of 512 MB. Stingy.
- Garmin Training Center does not allow a user to directly import a .FIT file from a location on disk. The API is to ask the device for a .FIT file, which in turn, means that files have to be saved to internal memory and not an SD card. Seriously? Sure, .FIT files are smaller than .TCX files (uncompressed XML), but with less memory, it looks like manual management is needed still. This is a known issue, see https://forums.garmin.com/showthread.php?t=14537.
- The .FIT format is more prone to corruption, and less fixable. A developer API offers some Java tools to help fix files, but it is not perfect. I have already lost some important ride data due to a crash. For the investment involved in an Edge 800 plus a power meter, the acceptable amount of data loss should be "zero".
- Where did the date display go? With the 705, you can press the Power key and it will tell you the current day, month, and year. The Edge 800 has no date related fields.
- It takes more "key presses" to get to some features on the Edge 800, and since it is a touch screen, there is no tactile feedback. Of course, being able to quickly get back to the home screen by holding the lower left "cancel" button is a huge help.
- Keys are no longer backlit. That was a nice touch on the 705.
- Seal for micro SD card feels less robust.
- Seal for USB port actually IS less robust. I noticed some corrosion (blue-white stuff) after a rainy ride.
- common firmware with Oregon series GPS. 705 was common to ETrex Vista series, 305 was common to other GPS.
- USB Mass Storage API like the 705.
- weird API for importing GPX and TCX routes using the "NewFiles" folder.
I hope that Garmin will address some of these shortcomings with future firmware fixes. The company does a decent job of getting products to market, but often lets them languish thereafter. For the cost of the Edge 800, us owners should be first-class citizens.