+1 on the replacement LED bulbs for the 4' fluorescent fixtures. Swapped mine out about a year and a half ago and the shop is at least twice as bright as a result. Haven't touched them since, and as others have said, they're instant on at full brightness, even in what passes for winter out here. Very satisfied with the swap, and would do it again in a heartbeat.
Last year I purchased 16 of the Feit 4' fixtures to light up a temporary spray booth. These fixtures come with 110V sockets on one end so that up to five of them can be daisy chained together. I found out the hard way, though, that trying to do more than five can burn out the first ones in the chain, so be sure to read the instructions during installation. Regardless, the lighting was very good, and every bit as bright as the replacement tubes. Another great Costco purchase.