my 2 cents worth...
I picked up a client about a year ago and inherited a VPN which connects his branch office to his main office. It has a CISCO 800 at each end and connection is via the Cisco VPN client.
In 12 months it has NEVER gone down. Runs 2 MS Servers, Including Exchange and a VOIP phone system plus about 12 clients. The owner also has a tendency towards fiddling....

Have worked with OpenVPN but for stability, this beats it by a mile.
Despite the fact that Cisco is not the cheapest gear around, as far as Total Cost of Ownership goes, I would think this is looking good. I certainly dont make any bucks out of looking after it. There is nothing to do on it. (But the MS servers make up for it !!!)

Dont ask me how it is set up - I never inherited the admin password and no one on site knows it but that is another issue to deal with when the need arises.