You can probably do a handheld two second shot with this.
Ahem... no. It's widely held that a steady photographer can hand hold a shot a one over focal length, e.g. if focal length is 100mm, you need to shoot at 1/100 sec to guarantee a non-blurry shot. Canon even uses this formula on their website. The Canon IS claims to improve on that by 4 stops. As an owner of many Canons with IS, I can vouch that this is complete and utter rubbish -- you're lucky to get one stop, or maybe two -- but for sake of argument, let's assume it's accurate.
Four stops faster than 2 secs is 1/8 sec. So I suppose that if you had a theoretical 6mm ultra-fisheye with IS, you could get your 2 second shot! Effective focal length on the 28mm using a crop camera is 45mm. So again assuming Canon's exaggerated 4-stop claim, the limit for hand held shots would be roughly 1/3 second with this lens. Back in the real world however, I'd guess the limit would be 1/20 or so.