I have never run into any issues with AT&T throttling or limiting, fwiw.
I transcode to 320 with JRemote and use it for hours everyday.
Hey Marco, my colleague is also an existing cutomer on the VIP package and still got hit with the throttling after 3.5GB data use, you are only limited to 350k (ish) though so it is still more than suitable for streaming using Gizmo
AT&T has
officially announced their throttling limits: 3GB per month for HSPA+ (3G and 4G) phones, and 5GB per month for LTE phones (or, at least, the iPhone 5, but it almost certainly applies to other devices as well). However, if you're just using it for JRemote, you probably wouldn't ever notice. Reported throttled speeds vary, but it typically ranges from 500kbps - 1mbps on LTE, and a vaguely defined "2G speeds" for HSPA+ devices.
If you're on an iPhone 5, and you get throttled to ~700kbps, your music streaming would still work fine. But if you tried to use it for other "heavy" tasks simultaneously, or things like video streaming, you could certainly see the difference.
Verizon is actually a bit worse in some ways and a bit better. Their
standards are a bit more vague, but reports are that it generally works out that users who consume more than 2GB in a month are subject to throttling, though Verizon supposedly uses an "intelligent system" to only throttle users when the local network is actually constrained. So, your mileage may vary depending on your location. Of course, recent reports are that
many of Verizon's bigger markets are now suffering under the strain (as AT&T was widely criticized for in the past), so this may be much more common now than it was a few years ago when Verizon's LTE network was new and relatively unstrained.
I can't speak to plans across the pond. If you're in Europe, you are almost certainly much better off with mobile data coverage, choice, and pricing than we are here, so I have limited sympathy.