My family has a house at the lake and I fish it often, both hard and soft water. There are plenty of big fish in the lake but they are not easy to catch or find.
Ice fishing access can be difficult however there are several places to get on. If you are going there I will PM you a location that you can get on.
The lake has a lot of fish in it but it is not the easiest place to fish. I really don't do that well there but I fish it because it is convenient.
As others have mentioned there are many inlets and outlets to be concerned about. Study a map before venturing out on any type of machine. It can be very dangerous if you don't know what to look for.
Aside from the dangerous areas mentioned above the lake does typically freeze up good and solid every winter. Usually it is frozen before winnipesaukee.