i've got one - its an Italjet Dragster 180cc (think scaled down Ducati Monster). unbelievable acceleration, it will eat most cars away from traffic lights unless they have a very quick car and they really try. discs both ends so it stops too.
http://www.italjetdragster.com/index.html
my girlfriend is a bike rider (suzuki 650 SV) and she has a 63 vespa that was rebuilt with 2004 mechanicals (ie. 150cc not 125, 4 speed not 3, electric start etc). its gulf blue and very very cool. think backdated 911...
we live in the inner city and they're fantastic. in summer, its nearly an hour to the beach with nil chance of finding a park in a car vs. 8 minutes on the bikes - park where you want.
i say go for it - and get an auto (ie. twist and go) as the continuously variable gearboxes are great for acc'n
ps. your wife will want her own within a month