I recently tried using my Tamron 18-200 lens for video, shooting handheld, and it looked horribly shaky. I've used my Canon 100mm L lens handheld and it looked fine. Is the only way to shoot handheld is with an IS Lens?

With a wide lens, you can shoot handheld without IS. It really depends on your intended style though as to whether it's smooth enough for you.

I've never felt the need for IS on my lenses.

However I aslo never shoot anything over 50mm without some kind of support, be it a tripod or shoudlermount.

If you're shooting with DSLR's handheld and you want it to look professional, you're going to want to use a lens with IS. I'm really steady handheld .. like rock-steady .. but no one is steady enough to remove micro-shakes.

I shot a portion of a music video handheld with my 100mm Canon and a Cavision hand grip I have and it worked great. But my Tamron lens looked like hell.

IMO, the difference in price is so great that you could invest in stabilization instead, like a solid shoulder rig (takes out the micro shake that alone...useful on lenses up to about 70 on a APSC sensor, or slightly more on a 5d) or monopod, or even better tripod.

IMO, the difference in price is so great that you could invest in stabilization instead, like a solid shoulder rig (takes out the micro shake that alone...useful on lenses up to about 70 on a APSC sensor, or slightly more on a 5d) or monopod, or even better tripod.

My sentiment exactly. Stabilization helps all of your lenses.

I don't know that it's really needed on even moderate wides. I shot at NAB mostly with a 35mm lens on a 5D2 and handheld rig and my frames were nice and sharp when I was holding relatively still. I would generally swoop in and/or out of the framing that I wanted to keep things dynamic. I wasn't tripod steady, but the individual frames shot at 1/60 were crisp. The shots with an 85mm lens weren't as sharp, but I didn't have to ditch any clips. In the end, it all had a good, consistent look. As you move beyond 85mm - and when you shoot close to objects - things get touchier.

If you're shooting with DSLR's handheld and you want it to look professional, you're going to want to use a lens with IS. I'm really steady handheld .. like rock-steady .. but no one is steady enough to remove micro-shakes.

All of my DSLR footage is shot with non-IS lenses or IS lenses with the IS swtiched to "Off".

Should I invest in a shoulder rig? I already have a glidecam

Should I invest in a shoulder rig? I already have a glidecam

I would for stability in those moments when dialogue is crucial. Look at the Manfrotto 561BHDV (monopod) or something like the Redrock Micro (shoulder mount).

none of lenses have IS, but I never shoot hand held either.