I just made the move from the 705 to the 800 this past weekend. Just to be clear, the reason I upgraded was because I was having trouble navigating new routes on the 705 after I upgraded the firmware to 3.3. I tried to reformat the drive, but I ended up bricking the 705 and would have had to send it back to Garmin for a repair. So instead of paying for the repair I spent the money for the 800, and I am glad that I did.

The display is dimmer than previous devices (I've owned the 305 and 705), however while riding for a few hours today I had no problem seeing the screen. I think that if I were riding later in the day, into dusk there might be issues clearing seeing the screen, but during normal daylight no issues.

I do think the 705 is no longer being supported. You can get it repaired, but I believe the 3.3 firmware is the last update you'll see for the unit. Plus, in my experience, the navigation is fickle. While loading a 28 mile GPX route the 705 would take 10-15 minutes to finish calculating, and although it did give me turn by turn directions there were times where the alerts didn't happen. The 800 handles navigation differently. Best I can tell (I've had the 800 3 days now) is that the 800 automatically converts the .TCX and/or .GPX nav file into the Garmin .FIT file format. That seems to load much faster and the turn by turn works perfectly, alerting you to a turn .12 miles in advance. I am very pleased with the mapping and the displays.

I bought the full package, although I probably could have saved a little cash by going with the device only. But I wanted another heart strap (my old one is getting a little gnarly) and the full package came with the City Navigator NT micro SD card. The cost for the device alone is about $450 and does not come with maps. If the mapping and navigation is important to you then you will need the City Navigator, or you use open source maps which you can google search and find a link for those. I have no experience with the open source but many have reported that they work fine.

You can have up to 10 data fields per page, and I think you can have up to 5 bikes in the bike list. Again I am very happy with the upgrade. Hope this helps, good luck.