As others have said, it depends on how and where you fly. In the
midwest, I have found that when the weather gets bad it can be hard to
find a FSS that has time to talk - "Arrow 27D, you're no. 4 for
weather" so the metars and nexrad become indispensable if you don't
have a stormscope. Around the great lakes, a stormscope won't show
snow showers. AnywhereMap (control vision) has a $2200 PDA system for
which you can get TAF, METAR, and NEXRAD for $30/mo from XM radio.