Great for its purpose
Like you are probably thinking, I was initially a bit skeptical of the fabric rack case design. How could it possibly be stable and protect your gear? Well, you have to keep things in perspective. This case is meant for local transport, not really meant to be loaded on a truck and dragged across the country. If you've broken your back loading anvil cases in and out of local gigs, you know how that just gets old. So for its purpose it's great, even more stable and hearty than I anticipated. The outer pocket is quite large and more than adequate to hold all your knick-knacks and doilies.
My beefs are quite minimal at best - the zippered face covers don't have a tremendous amount of protection but certainly adequate for tossing in the trunk. It's not likely you're gonna have bowling balls rolling around in there smashing up gear anyway, right? Also the zippered ends don't complete un-attach, which means they have to be folded under the unit when in use. That's ok if you have a flat top cabinet, it's stable enough. But I suspect if your cabinet had big chunky handles on top, the case would teeter around a bit. Keep that in-mind.
The carry handles are quite solid and strong, having some sort of solid dowel sewn inside. The only thing they should add is some sort of velcro wrap to tie the handles together, making them easier to manage. But man, I'm just picking...
The other thing I was a bit worried about was heat dispensation. I'm running an Ampeg SVT Pro and a BBE Sonic Maximizer and thought they could possibly generate a bit of heat, causing fuses to blow. But I can say after running for several hours at a time in rehearsals and a few gigs, it has not been a problem. BUT keep in mind that some units such as the Ampeg heads require a bit more space for air circulation. So I left a full space open between the two units. Certainly something to keep in-mind.
Overall, the Gator GRB-4U is a good buy, as long as you keep within its purpose uses. Use the hard cases when appropriate.