I have the Indivision ECS/AGA for my main machines. They work great.
I also have a XRGB2 for other stuff. I was going to use it on my Amigas as well but the Indivision is better. The external solutions might give you a picture on a CRT monitor but a lot of the time they don't look very good on the LCD screens.
Noise in the picture is the issue. Anything other than playing games can get annoying.