I've done this several times; it's a great way to see what different yeasts do, and to get multiple beers from one brewday. One twist I've added lately is to boil the bittering hops only. Immediately after the boil, I pour half the wort into a 3 gallon pot and add my flavoring hops to each batch when cooled to 190F. I just let the hops steep until the temp drops below 150 or so, then chill as I normally would. My first beer done this way has great hop flavor and aroma without much bitterness.