I assume "fully meshed" means each node connects to each other node, so each node has 109 tunnels (110 total). I also assume "Cisco IPSEC based VPN" means IPsec (rfc 2401/2411/etc.) and not MPLS-only. In that case, 120 is not 'large' according to the vendor community -- 'large' starts at around 5000 tunnels. I suspect that, in nature (or in the land of the Nanogians) that under 1000 is more like a 'large' one. On the other hand, drop one box with 119 tunnels set up and restart it and time how long it takes to re-initiate all 119 tunnels, and you may very well be unhappy.
From: "Tim Bass" <bass@silkroad.com>
We have a Cisco IPSEC based VPN with over 110 edge routers in a full tunnel-mode mesh, mostly 'big hunking routers' with average CPU utilization under 15 percent. The VPN is controlled by a single organization, under centralized admin.