They did some superb kits in the late 1970s-early 1980s. Among their jewels are the M-47 Patton tank and Leopard 1A2. Both are still the best variants produced of these two tanks. Also the M4A1 Sherman and Willys Jeep hold up well even today, although both have been surpassed within the last 5 years or so. Others like the Kubelwagen and Schwimmwagen were superior to the older Tamiya kits, but not as good as the newer Tamiya offerings.
If you want an M109 howitzer variant, you will be building an Italeri kit regardless of the box it comes in.
They did take over some very old Peerless/Max kits like the Dodge 3/4 tons and the old White Scout car. These suffer from age today. Some of their newer stuff is not done quite as well as the older stuff. Take the US 5 ton truck and 10 ton HEMTT, both readily available for inspection, but neither one done very well.
Right now Italeri also reboxes the old Esci M60 Blazer and M60A1. Both of these kits are superior to the Tamiya or Academy kits. Many times if you see a Revell of Germany armor kit and Italeri does a similar kit, it most likely is a rebox of the Italeri kit (M109A6 Paladin, HMMWV, Jeep come to mind).
Best advice is to ask about a specific kit. If you wanted to spend $15 on a Jeep kit, I'd tell you to bypass the Italeri kit and buy the Tamiya Willys MB. On the contrary, if you wanted the best Leopard 1 kit, I'd tell you to avoid Tamiya's Leo 1 and buy the Italeri (or Revell) Leopard 1. The opposite would be true for the Leopard 2A5, buy the Tamiya and bypass the Italeri.
Confussed? Welcome to the club.