Never used Dr. Tims but I've heard that it works well. I did use TSS not to long ago in my 40 gallon with fish in there and it did the trick in a little less than a week. I would have tried Dr. Tims but I just couldn't find it so I went with Tetra.
I don't know how easy Dr Tims is to find in the US but over here in the UK it could only be ordered via their official UK suppliers website. Since that supplier went bust it's currently impossible to get hold of in the UK unless you're willing to pay postage from Europe.
Actually I've just had a quick look and there is a website selling Dr Tims products in the UK - MarineAquatics.co.uk. Perhaps they're the new UK supplier. Although they're not listed as an authorised distributor on the Dr Tims site yet.