Just got mine and I love it. I looked around at other bike computers but they all came up short in the area of night visibility and half of my daily commute is after sunset. The 705 has a highly visible display and a backlight that can be set on all of the time. You can read up on all of the features so I'll just stick to the things that I was able to confirm since I've had the unit.
(1) The backlight is great and improves day visibility as well as making it very readable at night.
(2) The display is clear and sharp and very readable with seven data fields displayed concurrently.
(3) I bought the cadence/speed sensor but it works just fine without it as the speed sensing via the GPS works better than I expected based on some of the reviews.
(4) The GPS is very sensitive and can lock on to satellites inside my two story house.
(5) You can create a route by clicking points in mapsource and download it to the Edge with a press of a button.
(6) The turn by turn navigation works great, you get beeps .3mi and 300 ft before turns and the display shows instructions and arrows (no voice directions).
(7) It's very easy to upload the data to either Garmin Connect or the Garmin Training app and see graphs of all of all of your data.
(8) You can convert a trip to a course and use it as a virtual partner to ride against next time you make the same trip.
(9) You can compare two trips on the same route graphically for all data recorded.
(10) The positional accuracy is very good, probably within 30feet at most times. You can see clearly where I've crossed the road to turn left or stayed right and gone with the next light going cross-wise.
(11) The charger is the standard USB charger (that everything is standardizing on now).
(12) The heartrate monitor works very well and looks well designed (user replaceable battery unlike Polar crap which forces you to buy a new strap when the battery dies).
Okay nothing is perfect so here are some wishes ...
(1) Current Gear display/calculation. Not easy but it knows the speed and cadence so it should be able to work out which cogs I'm using. A display like (H-L)/(0-9) would suffice e.g. H/8 means 53/13 front rear.
(2) It could be cheaper. I paid $323.07 for a refurbished unit with HR/Cadence on eBay and using Bing and eBay bucks discounts but that's still 1/3 what I paid for my Ultegra equipped full carbon fiber framed bike. Only a mild complaint though because I'd rather pay that for the 705 than half that for a computer that can't be seen at night and offers no navigation assistance.
Overall rating right now would be 10/10 and trust me I'm pretty critical of most things.
I love mine. For me the best part is planning rides on the computer or downloading the rides others have taken and then getting out and following the map. This has really help me get out and explore more trails that I might have been hesitant to take for fear of getting lost.
I also think it is a great motivator to download your routes each ride and log everything very accurately. I too have the speed cadence, and really like having the additional data. I use it on my mountain bike without the speed/cad sensor and it still works great for that.
Overall I think it was very worth the money, but as with everything I wish it had been a little less expensive.
I'm not sure about Mac. I use mine with SportTracks and the Garmin website. Making maps on MapMyRide and others is pretty easy. Garmin has a USB driver download for Mac. I would think most of the stuff from the websites should have no trouble with a Mac.