Putting on/taking of bike shoes while on the bike

Are you using regular bike shoes? It's a lot easier with triathlon shoes: single strap, no tongue, made to stay open wide, loop on heel to pull them on.

Yes it does get easier and faster with practice, and yes there is a net gain of time to be had if you do it correctly.

I'll be the devil here and say that I am not so sure it is worth it.  I watched many races where putting the shoes on while on the bike has cost more time.  Crashes, mishaps, fussing, etc..  Even the pros.  Two seconds to slip on shoes then ride full on from the start or ride then coast for two seconds while on the bike risking mishaps.  Maybe if you are a pro, it is worth the risk to shave a second or two.  But in my opinion, there are plenty of other ways to make up or loose much more time then the shoe department. 

As far as saving time in the transition areas.  Make sure you aren't doing wardrobe changes.  Wear your bike and run outfit under the wetsuit.  No drying off and no socks, saves time.  Practice setting up all your gear in the back yard and run through the process trying to make it more efficient.

Look at your overall times in the race too.  Can you shave off minutes in your swim, bike or run?

I had similar shoes for awhile.  To save a wee bit of time putting them on and taking them off, I velcroed the middle strap shut W/O looping it through the eyelet.  If the bottom strap of the three isn't too tight, and the middle strap is just along for the ride, you really only have to worry about the top strap.  It's enough to work.