Target turrets for windage, not so much.
Depends on what you plan to do with the rifle. If you are looking to take deer at distances wtihin the point blank range of your particular caliber than no, they wouldn't be neccesary since your bullet never deviates more than 3" over and below. You don't need mil-dots for that application either. With a .308, 30-06, .270, 7mm mag etc, if you setup to be 2" over at 100 yards, you can just hold point of aim out to 300 yards and end up wtih a kill. (the kill zone of a deer is 6" from top to bottom of lungs/heart area). Since you hunting scope is parralax free at 150 yards, your 100-300 yard range is already set so you need not worry abotu that setting.
Now, it you want to compete in your local long range tactical course with multiple distances (200-600 yard targets) than they are very handy. Sure, you can count clicks, but if you loose count of where you are at during the match you are screwed. I would even add that unless you have perfect form and constant cheek weld that parralax adjsutment is also very important for such an application.
Basically you set your POA/POI to a set distance (usually around 100 yards) and zero the ring on the turret. So if you know the distance you are shooting is a 9 MOA drop, just spin that ole' turret up to the 9 MOA setting. It allows you to free your mind from counting clicks, and just spin the knob like you would to find a radio station. All that's left for you to do is try and slow your heart rate, squeeze and hopefully hear the steel target "ring".
I shot an NRA rimfire match last week and got to play wtih some nice Leupys wtih target turrest and some nice Leupys without. A match .22lr is POA/POI at 25 yards, about 3-4 MOA drop to 50 yards, and 7-9 MOA drop out to 100 yards. Consider that the small steel targets are 4" tall, you gotta be on the money with you aim. unless you had paper with you there is no way you could keep tract of your clicks in such a match ifyou were trying to count clicks, compete and score other competitors. Not to mention that you only have 2 minutes to take the 5 targets (same distance) and you may find that you need to add a few clicks during you firing time. No problem with a turret. just reach up and click.