Of course it is, you don't have to have a battery pack dangling off your phone, and it's pretty much instant. Only takes about 1-2 minutes max. My Note 2 boots up and shuts down very quickly.
I have an external battery pack charger, but I've never actually found that I ran out of battery during the day. I can just charge it for a bit if I need it to last the remainder of the evening. If I have to go out, I simply just swap it with a 100% charged one. Each battery lasts me just over 16 hours, and I'm a very heavy user, lots of things sync up constantly, I read lots of news, and browse the web, watch videos, call, text, email.....
Having a battery pack hanging from the bottom of your phone is immensely irritating, and isn't needed. You make it seem like it's a hard task removing the battery door, and swapping out a battery. Even a dimwit could do it relatively quickly. I even have an otterbox commuter case, and find I can swap the battery in under 30 seconds and put my case back on.
An external battery back is hardly necessary if you have a removable battery in your phone.