I have one. Bought it almost a year ago to use as a practice amp but I have used it in live and studio situations a few times.
It's good and loud, and has lots of great effects and tones. I didn't like the Line 6 FBV Express board though, so I passed on it.
If I need a specific sound I program it into one of the 4 memory channels (which is very simple to do) and call it up with the push of a button.
The DI out is great.
All around i've been very happy with mine.
I did try the LD 150 for a month before settling on the LD 300. I found it to be under powered for what I wanted it for.
TD