I wanted to post some of my thoughts and my experience using my first yeast starter this past weekend.
To start off, I have been brewing for around a year or so now. Half of this time has been all grain not that I feel either way impacts using a yeast starter or not. I had held off on using a starter for two reasons, the first being I didnt have a erlenmeyer flask and the other being I didnt have a single brew that had issue not using a starter.
This being said I have educated my self over the past year and have added things like using a Oxygen tank with stainless steel wand with .5 micron stone to ensure a top level of oxygen for my yeast. This made a huge difference and only pushed me further back from any intention to use a starter.
Since I have started creating and playing with my own recipes using all grain I have read up more on yeast and how it impacts flavors. This was the final straw for using a starter. Yes, anyone will tell you that using a starter will give a fast and better (not to mention quicker) fermentation but its not until you get into the science of the yeast and how it effects the flavor with what it produces as it converts your wert to beer. Not to mention pitching 3 times as many good cells as normally comes in a vial of yeast.
Cosmetically the difference in air lock activity is 3-4 hours from pitch with starter and 12-24 hours without. That makes me happy even though I know fermentation can be happening with out the airlock bubbling. But in all the beers I have made not a single one didn't have active bubbling. I do not brew recipes that don't allow fermentation temps between 65-75 degrees so colder fermentation temps may impacts this but it don't really matter as I check with my hydrometer and follow my recipes time table.
My end thoughts are this:
Do you need a starter, no you don't. You just need to pitch a proper amount of yeast and if your doing 5 gallon batches then a single vial has always worked for me.
Should you use a starter if you can? Yes, always! Its just a matter of good science to ensure the best tasting beer. A proper flask is cheap as is light DME and no you don't need a $100 stir plate. That is a luxury. Not to call a magnetic stir plate a gimmick because it is not. Its used in almost every lab and gives consistent results. But like many of the fancy toys in this hobby you dont need it, but it can make your life a little easier.