First yes the access will work with the Atlas .
I like the Atlas but yes some of us have had problems with certain features . The UV sensor on mine and other read to low . But once again a ton of people haven't had any problems with the UV sensor on theirs .
I run both my old 5-1 and Atlas and I feel the Atlas has more accurate readings then the 5-1 for wind, temp , humidity .
I like the fact that you can use the wind adapter so you can have the main body lower on a pole and the wind part higher on the same pole . I haven't hooked mine up yet because of the weather but I will when it warms up .
My biggest grip with the Atlas system is the display . You cannot use your 5-1 displays and the new Atlas display has no battery inside so if you unplug it or it loses power all the readings are gone . Why they didn't add a battery to it is beyond me . Also there is a " sleep feature " to have it go dim at night and go bright in the morning but I found out even when dimmed to much light come thru to have the display in my bedroom . But that's me I don't want any light at all in my bedroom .
All in all I'm probably 80% happy with the Atlas system I feel it could be better but for the price you can get one on sale with the display it's alot cheaper than you can find a comparable system with the same features .