I don't have an MES, but have read that they tend to smoke intermittently due to the heater element cycling on and off. This causes a heat/no heat situation with the chip tray. There are modifications that can be done to correct this. DaveOmak, if I recall correctly, did some rather extensive mods to his MES and it all made sense when I read about it.
As for smoke intensity, a heavy smoke si OK for short periods of time, but for those newer to smoking, it can be difficult to control the amount and duration. I use a heavy smoke a lot for larger cuts of meat, but not the whole time...usually at the start, and for no more than an hour. Smaller cuts of meat don't take very kindly to that sort of treatment.
The main causes for a bitterness from the smoke are improper ventilation of the smoke chamber. Stale smoke is not your friend. If you get a numbing/tingling sensation on the lips or in the mouth, that's generally the result of creosote from a heavy smoke and too little draft/ventilation. The bitter taste is also due to the same causes, and is your first sign of problems...the numbness/tingling will occur in severe cases.
Here's Dave's Mod Thread...some pics don't appear anymore, but I think his explanation will cover most of it. There's a second post on the more complete set-up farther down the page, as well. He did more mods as well. If you're interested in making the smoker a whole lot better (none ever really seem to be perfect, and I don't mean just MES), check in the electric smoker forum for MES mods, as there tons for better smoke output/control, temp control, etc.
http://www.smokingmeatforums.com/t/...g-element-using-an-incandescent-dimmer-switch
Eric