I thought it would be an issue with me, but with the online storage it really made it a mute point. I too used it with my Treo 650, Treo 800, and my FrankenPre2. I got the 16 gig version (only one I could get on Sprint at the time) and I have never got it full. Stream my music instead of loading it up with MP3. I dump the pictures off of it once but have not done so in 9 months (I take a lot of them). For apps, I just keep the ones I need. I don't have many games on it because that will eat up the 16 gigs. If you get the 32 gigs, you will have plenty of space.
First, it has no SD card slot (which is one thing I missed moving from Treo to Pre many years ago).
After one year, I have not had much of a drop off in battery power. The one thing that kills it is your reception. Since I have Sprint, it bounces in and out of good and poor coverage which eats away the battery. I do have a charger pack on the side, but I usually get 16 or so hours with moderate usage. I do wish it had wireless charging but I think it was dropped due to the Google Wallet. That works great so I don't miss the wireless charging that much (but I would love to see it when it comes out)
Second, it doesn't have a removable battery (and there's just something reassuring about a last-resort battery pull - not to mention spare batteries).
The size and shape to me is great. It feels good in the hand. I was checking out other smaller phones but when I noticed the size of the phone was shorter than an slid Pre but thinner, it felt good. I liked the S4 Mini shape and size as well, but the vanilla android was a much better interface than the window dressings that Samsung puts on the phone. If I were to get a Galaxy, I would blow the ROM and install CM11 on it.
Lastly, it is bigger than the S4 Mini. Not by much, but it is noticeable to me. I always thought the Pre 3 was just the right size for me. The S4 Mini is a bit taller, but it is almost exactly the same width, and it has a more rounded shape like the Pre line. .
Now, my biggest complain of the Moto X was the camera. It is slow and not the greatest but you can still manage to get decent pictures. I am looking forward to the X+1 when it comes at the end of this month. It will be a tad (5.1" 1080p screen vs 4.7 inch 720p) bigger screen and 2900 battery instead of 2600. The Notifications on it on the lock screen are changing as well. They will be displaying across the top (it sounds like how webOS did it from the bottom, then again the same guy who did the UI is doing android now).
One other thing, you can custom build the Moto X. There are several wood backs that you can get along with a bunch of other colors. You can customize the buttons, and upgrade the memory.
Another good feature of the Moto X is the wrap around glass on the front of the camera. it's very durable and last year when the tested Iphone 5s, Galaxy s5, HTC One, and Moto X, the X was rated the most durable phone from resisting damage.
Good luck in choosing your phone.