The recomended speed is as fast as you can get. Really, it depends upon the application. You also have to keep in mind that the stated speed of DSL (or most other high speed connections) is the speed of the downstream - data coming toward you. The upstream is only a fraction of that, DSL is commonly 768K downstream/128K upstream. If the other end of the VPN is also connected with DSL, you are limited by the upstream on both sides. Other problem is if you saturate your upstream bandwidth, the downstream can get choked down. That's a problem with TCP in general, not just DSL.
Main things you have to look at are 1) How much data do you have to move at once? 2) How forgiving is your application, will it care if there is a delay in sending information either way? 3) How much are you willing to pay for better performance?
Next thing, NetBios doesn't route across subnets. Period. Some try it, but I have never seen it work well. Even if your router does handle it, your VPN client also has to route it from the VPN if to the LAN if, and it doesn't happen. You need a lmhosts file on your client.
What happens when you get disconnected from the VPN? Do you get an error message? If so post it, and be as specific as possible.
