I've battled multiple times with Seismitoad in my team, and I must say it was never a loss in my team. I have changed it for Mantine because it suits my team better, but if Seismitoad fits in your team, you should definitly give it a try.
As JirachiCelebiMew said, it's an awesome pokemon with lots of sets, that can still surprise most players if you play it well. I like to use it for it's immunity against electric and it's base power. I have seen it being used in many different sets, so it's a shame it isn't being used more :(
<+chieliee> .tell chielieee HELLO MYSELF
<skybot> chieliee: I'll pass that along.
* chieliee is now known as chielieee
<+chielieee> sup brah