Yes the firework looks crappy, however try to get a circle of say 6 people
and make them all cast at once:P it's a little better, still needs fixing
though.

The level cap (5*(lev-15)) still stands, but they will fix it soon in the
patches. Finally I guess we got the idea through verant that the skill is
capped, took a while. I suggesst you wait till level 30 before start
tinkering, it will cost a lot of time and money, and by then you will know
for sure the skill cap is at 75 if it's not fixed and some nice wis/int gear
i hope.

Gagaliya Ba'La'Boom!
Master Tinker
Lev 40 wizard
The Claw of Nagafan