Pros: extracts, if homemade, are great for tasting trials as they give you a great idea of what/how much of your extract to add...if you choose to add it.
- if you are fortifying, the alcohol you used as base for your extract simply blends in
-you are only limited by the access to extract ingredients and your imagination.
You will find yourself using them in baking, in cooking, in coffee....even DIY reed infusers.
Cons: it is an extract and some feel that is cheating. My view on that is, if homemade it is all natural ( one would hope you are not using synthetic anything) and it is YOUR craft. If you enter in competition then be sure to disclose if rules require you to do so.
I have not used the LHBS variety of extract because the wines I have tasted that use them have always seemed overdone to me. They may have a better impact in brewing, perhaps not so much in winemaking. BUT, I also believe you get what you pay for. Use only the best extract you can find, and afford. Ask others which extract they prefer for x-flavor and where do they source it. What have they used it in, and in what ratio. A classic example is a chocolate extract: compare LHBS or such to that of StarKayWhite brand chocolate extract. You will never buy another chocolate extract again. That brand is considered by many professionals to be THE brand across the culinary planet. And even normal people can easily attain it, with the click of a mouse.
Tasting trials are key. Do not ever just add x-amount because that is what someone told you. We may share what works for us, but is your wine the exact duplicate, is your extract the exact duplicate? Temperature and S.G. and type/style of wine will impact the outcome of the extract. Be prepared to experiment. You never know when three little drops per gallon will send your palate on a rollercoaster ride. Speaking for all extracts.
Sorry for being a windbag.