If you like Yngwie than it's great. I'm not big on the Bridge pickup and would probably change it for a Tone Zone S (single coil spaced TZ). As for being a one trick pony, that depends on how well you adjust to the scalloped fretboard.
No, they are not a one trick pony. They take a bit of work to get the best out of but are quite versitile. The USA ships with a 3 position selector but it;s easy to wegde to get the in between sounds which are pretty sweet.
I would not have one as my only guitar but they are totally different in feel and sound to every other guitar out there and for this reason I would say go for it.
You need a good pedal (I use a compressor and sometimes a DS-1 as a boost) to be able to do the rock thing and I don't think you would get a good death matal sound out of it.
Chords can be a bit tricky to play in tune until you get used to it. I still struggle a bit with the open D when I have been playing my other guitars for a while.
21 frets is also an issue for some people.
I love mine, don't play it as much as my JEMs but when I do I really enjoy it. they look soooo cool as well
The bridge pickup IS a bit trebly especially in contrast to the neck and middle pups. Making friends with your tone control will be a good thing if you get one. When clean it's not a problem but when you get a bunch of gain on it it will start to become a problem (but that can be worked out!!!!)
I find that the Malmsteen strats are not so much a one-trick pony unless you only play Malmsteen on them....