I have used Witopia for 7 years now and was generally happy with it until recently. They have excellent customer service and you can chat with them online 24/7. The online chat has only ever been down once or twice when the government was cracking down on VPNs and trying to block their service. They had to close the online chat due to the high volume of requests but were still answering emails. They did manage to restore their service within 1 day and never asked their customers to pay extra money by introducing addons necessary to make their VPN work in China.
The only complaint I had was that they blocked access to bittorrent sites several years ago. They didn't block P2P traffic, rather they blocked access to the torrent sites (torrentz, pirate bay, etc).
The reason I stopped using Witopia is because their service kept getting slower and slower to the point that I couldn't use it any longer. They have very few PPTP servers that work from China. If you contact support they can give you a few. The majority of the IPSec servers are working but most are very slow and the connection is not stable (you need to reconnect often).
I am now only using Witopia for doing speed testing which I will continue doing until my account expires.
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