i've only have 50:50 fios a month, but have already used a vpn in a vm, off a pc tap, and off my router's firmware, and thus far have not found any additional issues beyond those already native to vpn use itself.
one thing that surprised me after coming from a 50/5 coax to 50/50 fiber, is despite the greater upload, when i p2p those other networks i'm connected to do not exploit my upload as much as i had expected.
so if your plan is to p2p seed a lot, you may be better off using a vps off a cloud server, not a vpn off some client pc.
I have used a couple different versions of Cisco's VPN clients - the latest being Cisco Anyconnect and just recently started using Barracuda Networks VPN client. They both seem to work fine.
I can't speak to trying to run a VPN server using FiOS though, if that's what you mean.
any speedtest sight is a naive and misleading way to test a VPN
a more accurate method is to p2p commercially seeded torrents
such as ubuntu clients, then see how consistant your MB/sec is,
then multiply that number by 8 to get your MBPS rating.
fios gigabyte customers may be disspointed to learn that most
VPN outlets will only give them 13MB/sec.