I also like the .357 SIG. I had a Glock 33 back when they first came out in the mid/late-'90s, and shot it a lot.
The round is super-reliable (you're shoving a 9mm pole into a 10mm hole) and plenty accurate. It's feisty, and it took me about 500 rounds to stop flinching from the concussion pressure wave (similar to that from a fast .357 mag bullet) that hit my chest everytime I clicked the Glock's trigger rearward.
And I couldn't get my wife to even consider picking the G33 up (unlike my G26, which she'll at least try). Crowds would gather when I'd shoot the pocket rocket, but no one really wanted to try it.
The price of ammo is tough. It's come down some, but you'll still not find .357 SIG ammo anywhere near as cheap as 9x19. Just think of all the extra practice you can squeeze in (and think of all the 9x19 I could have fired instead of the 2200 rounds of .357 SIG that I did fire . . .).
Also, however, there is the issue of bullet set-back. Initially, at least, you couldn't find .357 SIG ammo with a cannellure to hold the bullets. This is an important consideration in any bottlenecked handgun round (just look at the mega-crimps on the Sov's 7.62x25 rounds to see what I mean), but it seemed especially a concern at the close-to-the-envelope .357 SIG pressures.
And I experienced bullets setting themselves back. Some of them way back.
Now, this problem might have been solved by the manufacturers, but to me it was a real concern at the time. I've been thinking about picking up another .357 SIG, and have posted a question about whether the set-back issue has been resolved over on Glock Talk. No useful answers so far . . .
Anyway, I don't have disdain for the round, but I'd say that pricing issues together with the lack of an ability to fire moderate pressure rounds are its biggest albatrosses.