I used clamp on forks for many years and accepted them as a decent trade-off for the cost savings over proper pallet forks. They do give you a good bit of versatility, but obviously have many limitations. As time went on, I began to hate them more and more. Finally spent the money on SSQA forks and wish I hadn't waited for so long.
One thing I haven't noticed in this thread is the reduced capacity due to how far forward the bolt on forks sit. You can't use your machine's stated lift as a guide since that's rated at the pins. With bolt on forks, you're sitting 3 feet or more forward of that (whatever your FEL bucket measures). I use a carry all seated in the bucket and strapped in place. It works for carrying brush or small loads, but I can only lift a couple of hundred pounds that way.
I've worked out a way to remove my FEL bucket and mount the carry all at the pins which should make things a lot better, but I haven't completed it all yet to test it.