[The Great Mahoo]

The retention strap can be nice, or it can be a pain. Personally, I don't care for them on my daily conceal rig; the normal retention of the mouth is good on most well-fit holsters, especially with IWB. Retention straps are nice, however, if you find yourself jogging up/down steps or making bending over a lot. For typical day to day use, I have never found it to be an issue not having the strap.

For holster style, there are many shapes and sizes, made to accomodate many different preferences. I prefer small holsters, using Slides for the most part for my OWB carry. These are just short holsters which secure the gun around the trigger guard and chamber, having an open bottom through which the barrel hangs down. This allows guns of various lengths (provided they are similar guns) to be used in the same holster, doesn't hand any lower than it needs to (no extra material to stick out) and lets the holster be easily hidden if empty (when going where a gun is prohibited, but I don't want to take the time to remove the holster.)
I am also a fan of IWB carry, especially tuckable holsters to allow me to conceal in most any mode of dress.

As for Galco and Bianchi, they both make excellent products, and best of all, are readily available for most guns. I actually was looking through their product lines the other day, and noticed their prices have really gone up from what I remember buying my last one at. For about the same price, or a bit more, you can get a custom fit holster from one of many great places. I have a tuckable IWB from K&D leather that is among the nicest I have ever used, and have been debating on a second for a new gun. If you want to look into some other dealers, I'm sure many of us can make some suggestions. Keep in mind, going this route usually means a long wait (3 weeks to 6 months) where as Galco/Bianchi are usually stocked items easily had within a few days.