The AR-70 and the AR-70/90 are really two different guns. The AR-70 that was offered here in the USA was the original AR-70. The AR-70/90 never made it here as it came out in 1990, after the import ban.
The AR-70's had some durability issues. Seems the stamped receiver could get twisted if it was roughly handled. Obviously at the current prices, they probably don't get abused too much. There were some other problems with the buttstocks coming loose, and a few other minor things.
It was never really successful and lead to the development of the AR-70/90 for the Italian military to be their new NATO caliber rifle. It pretty much solved what few problems the original had and by all rights is supposed to be a fine rifle.
As pointed out, mags are VERY expensive. Like in the $100 each for a 30rd mag price zone. I believe there was a mag adaptor for it to take M16 mags.
I saw one with one mag for $1700 last year, in VG condition.
Ross