This may a useful site to some:
http://www.tramsoft.ch/gps/garmin_dakota20_en.html
It's a shop, and it's foreign so I doubt anybody here will use them, BUT - it was quite usefull in seeing the features and screenshots of various different Garmin devices, a lot of the search results looking for info on Google didn't seem to go indepth.
Although I use Sportypal, and would still recommend it for use on a phone, I've talked myself into getting a Garmin Dakota 20.
It was a toss up between that or an Oregon 200.
The Dakota has a smaller screen, but is supposedly a bit brighter, it has the full compass and barometer same as the 705, and according to Garmin's site, it will take a HRM and cadence sensor, not overly bothered about that but just incase I come over all strange later on and get sporty about things
It also has a micro SD slot for added memory, but there is already 850mb on board, it also has USB connectivity and takes AA batteries.
There is also a Dakota 10, which seems to be the same, minus the compass and altitude barometer thing and the memory slot - not sure about the HRM with that. My main concern was the memory slot, not sure how it would pan out being limited to 850mb.
Just need to look into the maps now.
It looks like it needs City Navigator to get turn by turn directions for road use, is there a free alternative, ie does the open os stuff allow for turn by turn?