So, why after all this time, this happy beer making?
I am forever worrying about getting the inside of my chiller clean and sanitary, it's 8mm microbore copper tubing and there is no way of getting all the liquids out of it unless you connect it up to a compressor to blow air through it (which I do), this is a faff.
On a brewday I first have to flush it through with oxyclean, I then have to rinse it, I then have flush it through with Starsan, I then collect the first runnings in a jug and discard, for some reason, even after all the cleaning, this often has a noticeable green verdigris tinge, urgh.
As for the immersion chiller, well, if kept clean all that needs to be done is for the chiller to be inserted into the boil kettle 15 minutes from the end of the boil, that's it.
Time and the effect on hop bittering and aroma.
The throughput of 10mtrs of 8mm microbore is pretty low, this mean it takes ages for the boiler to drain. All the while the wort is sitting there at nearly boiling point and the hops are continuing to isomerise and the volatile aroma oils are being driven off.
According to this BYO article, "Alpha acids will continue to isomerize after flameout until the temperature of the wort reaches about 175 °F (79 °C)."
Therefore getting all the wort down to below this temperature, as quickly as possible, will ensure that this stops, and you should have a much more predictable level of bitterness. It should also help prevent the flavour and aroma compounds from being driven off, indeed according to the same BYO article, if you hold the temperature between 160–170 °F (71–77 °C) you can find increased aroma and flavour is obtained.
This level of control is just not available with a counterflow or plate chiller.
It might be that the optimum is to use the immersion to drop the temperature to halt bittering, and then stabilise for 30 minutes while an additional amount of hops is added purely for aroma and flavour. Then both the immersion and counterflow could be used to get the beer down to pitching temp as quickly as possible, clearly there is room for much experimentation!
Oh I estimate I lose half a pint to the chiller.