we haven't tried but the primer annealing temperature's in normal PCR is around 50-60oc in that temperature taq polymerase wouldn't be disturbed as the best activity temperature for taq polymerase is around 74oc. So it may efficient enough beyond that temperature's. 

Efficiency will be lower at 60 than 72, but is usual to run PCR reactions at 60. Many real time assays (eg: Taqman) are developed for running at 60 degC.

If you look at Fig 2 in Chien et al. (1976) you should be able to work out the efficiencies at various temperatures - see linked file.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC232952/pdf/jbacter00316-0528.pdf

Thank you guys, The information you provided are very useful.

Hi I use TAQ polymerase on denigrate primers at 40C and get beautiful bands. I also use TAQ on a wide range of primer sets for antibiotic resistance from 48-56C. 

which is the polymerase working at the lowest temperature?

I was wondering the same thing. Thanks for all the answers, I will try at 55C, let's see what will happen.