i've got a t-board and a longboard from insect skateboards. i got more use out of my longboard than the t-board. on average i traveled 3-4 miles on my longboard thru my neighborhood. on the t-board, maybe a 1/4 mile in a parking lot if i was lucky.
the t-board is fun to ride, but lugging it up a hill sucks. the wheels wear quickly too. i've had problems with the hubs breaking on the wheels. it makes an annoying clicking sound.
you'll cover more distance on a longboard than a t-board. you're basically limited to going downhill on a t-board. with a longboard you can go downhill, flat and uphill (if you kick which IMHO is good training).
on a t-board, you can't ride with an alpine stance. feet have to be 90 degrees to the board. kind of defeats the purpose for alpine training, doesn't it?
my longboard is much faster than my t-board. everytime you turn on the t-board it slows down. i can pump it for short distances to the speed of a slow walk. on the longboard i can pump it almost indefinitely.
i think the t-board is overrated (i bought into the hype). i don't see bomber advertising t-boards anymore.
not sure about a carve-stick. looks fun.