I bit the bullet and bought a tooth bar for my FEL. It just arrived yesterday, I installed it this morning and I've already put it to good use. I removed five tree stumps today, first by pushing them over with the FEL and then scooping them up and out. The tooth bar made this much easier than it had been previously. Not only was easier to break out the roots, but it also added additional support by effectively adding length to the bucket, making it easy to haul the fairly large root balls away, as evidenced in the photos below. The teeth greatly improved the digging ability of my FEL, especially in the soil we have here in Southeast PA, which is mostly clayey loam and fractured shale.
After researching offerings from the various manufacturers, I settled on the United Steel Works unit and I'm glad I did. This is a serious piece. It's a 48" bar with five Pengo forged "tiger teeth" and it weighs 70 pounds and is extremely well-built. All I had to do is drill one 1/2" hole on each side of the bucket to attach it. I bought it through their eBay store, "agrindustryinc". It was listed at $244.99, but they generously accepted a lower offer. I called them on the Saturday that I ordered it to provide them with the exact dimensions of my loader bucket, because they make them to order and will custom-fit them for you, as well as provide other options, such as various tooth styles (3 to choose from), extra teeth, etc... If you're not an eBay fan, you can go directly to their website to order. http://agrindustryinc.com/ The bar arrived just shy of 3 weeks after I ordered it.
Not only a great improvement, but lots of fun. Looks cool too!