I switched from Drakes to Flows about 3 years ago. The reason for switching was NOT in fact the speed of getting in (while we are on the subject I shall note that while the speed of getting in with Flows is faster than straps, the speed of getting out is slightly higher). The reason for switch was the fact that I didn't like how my pressure would change from ride to ride on straps. I'd strap in, ride a few hundred yards, then realize I need more stiffness and add a couple of clicks. I'm sure this happened to everyone who rode straps for any significant period of time. The model I picked was Pro FS. My initial impression was this: very easy to get used to but I couldn't get the stiffness I wanted. With time I realized that A) Flows generally give you more control for less pressurized feel than regular straps, and B) Flows require a LOT of adjustment to get dialed in just right. In other words if you try your buddies Flows it's like you are trying your buddies heat molded boots - not gonna work. Once B) is solved they are very enjoyable. The latest generation (NXT) solved B for most cases I've encountered.
One other problem I've encountered during use was with my wife's Amp 5's - the lock handle would sometimes go off after the jumps. While this would not open the binding (as you push out the highback it locks it further) it was extremely annoying. Adjustment with a screw driver would solve it but only temporarily. In 2006 they've redesigned all the locks and solved it entirely.
Bottom line is: it's a matter of preference what you ride - I'm still OK with conventional straps and I like the feel of them. I just prefer Flows for consistency.