I can give you my opinion, for what it's worth, as a new user who migrated a few days ago from Galaxy S2. I actually wanted an S4 but my finger slipped on ebay and I got an S4 mini instead. I've got a 64Gb SDcard because I carry a lot of media files.
Like you, I thought the custom rom market for the S4mini was a bit weak. But actually it's not bad, considering the few weeks since phone release - we have a way to root and a few 4.2.2 and 4.3 roms available.
First thing I did was to root and remove samsung bloatware with a script from xda. Then I reformatted my sdcard to fat32 'cos I want to be able to mount it in CWM. Now I'm going to wait tile some stable 4.3 roms emerge and CWM mounting of exfat disks is fixed before deciding to stay with stock or move to something else.
The phone is pretty good - a decent size, easy to hold and operate, decent screen, good camera. It's a bit expensive and the 8Gb memory is a pain but at least it has an sdcard slot and replaceable battery which many competitors don't.
tip: buy the i9195 (LTE) variant, I think it's more future-proofed than the others.
Good luck with your decision