Very busy road.. it's the N3 after all. Traffic at all hours of the day and night, you'll need very good windows.
The stretch between Navan Road junction and Cabra shops is by far the nicer part - houses are generally semi D and set back from the road. Between Cabra shops and Phibsboro, the houses are more likely to be split up into bedsits.
For for ASB, Cabra is generally a lot quieter than it used to be, but I'd imagine there would be an off-chance of some random problems occurring, as there could be anywhere close to town. I'd say that security could be a bigger problem - a nice, big house such as some of these are could be a target for break-ins in a largely working class area.
As for schools, I can't really say.. there's an Educate Together down Grangegorman, which is where I'd send my kids (if I had any and lived in the area).
Other options for you in the area could be Charleville Road, Rathdown Road, Cabra Drive or the roads around Skreen/Nephin Road (further up, off Navan Road) - which are slightly further from town, but probably quite a bit quieter, and also right beside Pheonix Park.