Many many many many people recommend that you use "Extra Virgin Olive Oil" for vinaigrettes... I myself do not. Olives have a definite flavor of their own - one that I absolutely love - but not in mnost dressings.
As many restaurants and fine chefs do, I use a neutral flavored oil in the majority of my vinaigrettes. Canola happens to be my workhorse. It is delicate enough to let the flavors of the other ingredients come through, and doesn't clash with it's own flavors.
Here is my run-o-the-mill vinaigrette.
2-T White Wine Vinegar (I use Red for heartier salads)
1-T Finely Minced Shallot
1-T Minced Chives
1-t Minced Tarragon
1-t Minced Flat Leaf Parsley
2-t Dijon Mustard
Good Pinch of Salt ("Pickling Salt" dissolves easiest)
Good Pinch of Sugar (Balance of Salt/Sweet/Acid is important)
Freshly Ground Black Pepper - To Taste
5-T Canola Oil (Sometimes 6, Depends on strength of the Mustard)
Put it all in a small lidded jar or a screw-top ziplock container and shake vigorously until the liquids emulsify. Let it sit for 15-20min for the flavors to spread/develop then shake again before use.
The trickiest part to a fantastic vinaigrette is getting the correct balance of salt and sugar. Make a practice batch and slowly add more and more salt tasting between each addition until it gets over salted. Then you'll know where the fine line of fantastic lies.
Anyhoo... try using a neutral oil like canola. The herbs I commonly use above are of course optional, but add some interesting complexity - be careful of the tarragon though, it can be overpowering. [/quote]
I think it's an individual palate thing.
I pretty much only use a flavorful extra virgin olive oil for vinaigrette dressing --
because of its assertive taste. The best part about a vinaigrette is the olive oil, IMO. And good vinegar. All else is superfluous (most of the time).
I personally don't care for loads of herbs in my vinaigrette. But still, I think an assertive oil is perfect with them, unless you really are aiming at making the herbs the focal point instead of a back note.
I might use canola oil or grapeseed oil for a salad dressing but not a simple vinaigrette.
Everything else you say I totally agree with, particularly the importance of the sugar and salt and their balance. Vinaigrette without them will taste flat and harsh.
I would suggest experimenting with different oils and vinegars -- just don't use white vinegar.