The battery thing comes in handy pretty much anytime I go downtown (Chicago) or am on vacation. I take a lot of pictures or use my phone for nav/finding places to do things in areas I don't know. Some of these areas are low signal which draw even more power (changing carriers from Sprint should help this) and I'm away from a car/home/hotel for extended periods. I've been caught more than once trying to look up train schedules where my phone is on %1 or having to borrow a phone after an event because my ride was on the way and my phone died. With my Evo3d on my last vacation I had 3 cheapo ebay batteries that I bought with a standalone charger for like 12 bucks. I could go for days without having to plug in. Other times I am near home but I'm doing something in the morning then have to go to work at night. I'm not at home or in the car long enough to charge so my phone is dead. I've turned to portable chargers but they are much more inconvenient. They are bigger than a removable battery and require a cable to be plugged in. Also you lose some efficiency transferring the power. With a removable battery you just pop it in and it's 100% no need to work around a cable for an 90+ minutes while it charges.

For the card I use a lot of media (tv shows/movies/music/podcasts). That takes up most of my storage. On my old phone I could load up multiple cards and just swap them. I also like to flash roms and some upgrades require wiping the entire memory (including the "sdcard" partition on the flash). With a memory card I could use a secondary card to flash and know my personal data is safe where I've been burned by a few roms that unintentionally overwrote the partition and I lost files. This means that now I have to do a full backup of my personal data before every flash which is a huge inconvenience. There are sync apps but when you're flashing roms constantly it's a bit of a pain and time consuming to restore everything.