I have -- in a seam sealed Black Diamond Firstlight.
Now, to be fair, the BD Firstlight is marketed as "highly rain resistant", not rainproof. Talking with a BD rep, the tent fabric can block out 5 hours' worth of rain.
In my backyard testing, the tent kept out heavy rain for about 9 hours -- substantially longer then expected. However, once water started to seep its way in, that was it. Water wasn't just coming in at one or two places where you could sponge it off -- it was really seeping through!
To me, an EPIC tent is great for places where rain is either seasonal or quick moving. But if there's a chance of a day-long downpour (or worse), then bring something that's truly waterproof. 9 hours might sound like a long time, but say it's 3pm and it's been raining hard. Do you put up your tent right then and there -- and risk getting soaked by midnight if rain continues? Or do you tough it out in the rain and wait until 9pm to set up your tent so you can remain dry through the night and into early morning? I wouldn't put myself between a rock and a hard place like that.