In the North Dallas area the places that I've found to be the best are
Artisan Vapor (They have several DFW locations) and
Wickedly Hot Vapors in Plano and my absolute favorite place is
Uvapez in Allen. All
three of these shops have excellent selection of gear, a good selection of juices, reasonable prices, and very friendly and helpful people. (Uvapez website is a work in progress though)
Other North Dallas area shops that have a good selection of stuff but higher prices or not so great staff are
DFW Vapors (3 stores in the area),
Royal Vapor in Allen, and
Dragonfly Ecigs in the mall in Lewisville.
I've only been to one
vape shop west of I35, but I must say that
Freedom Vapes is a very good store, even if the employees tend to show off their latest and greatest RDA foggers a bit too much. They were very helpful and had good selection and prices.
EDIT: I've linked to all of their websites so you can check their selection and prices without having to go there.
Note that Uvapez is a new store and their website is still being built out, no online shopping yet, but they have a really great selection. $11 per 30ml juices and $41 for a Tobeco Kayfun with plenty in stock, good shop and good prices. It's the only shop I've seen that had a 26650 Tesla VV mod in stock. (Biggest freaking ecig mod I've ever seen. Made the SVD look like an eGo)