I debated getting cowl lights a while back. For the price of the cowl mounts and lights, you can upgrade your headlights to HID/LEDs, buy the OEM air dam, and swap out the Hella 500s that come with the OEM air dam for some LEDs.
I did all that for $380 total and couldn't be happier. Now if you've already got roof lights, upgraded headlights, and bumper lights, and you still want more light output, then yeah the cowl lights might be worth it.
I love my cowl brackets, have my lights angled slightly outward for a wider field of view, helpful when turning corners on trails at night. I don't have rigid lights though, those are really a personal preference, If you have no problem dropping that kind of cash on them, then I'm sure you'll be happy with them. I opted for off brand lighting and works well enough for what I need them for.
Whether its "worth it or not" is completely up to you and how you plan to modify your rig and where you want to throw light. I got the cowl light brackets and Baja design squadron pro lights and am very happy with the outcome. The added view angle (toed out and further back) lets you see a lot more than lights on your bumper. The install is definitely not easy. Did it mostly myself and took a couple hours. If you plan to get the brackets check out the lower posts of the first page of my build for information and all the clips your gonna need to make it easier. Also it helps I got the BD lights shipped for less than those rigids.