My setup:
3DSXL FW 9.5.0-22U
Powersaves Pro 3DS
Sky3DS with brandless 32GB class10 SDHC micro card. (try not to get more than 32GB because of 31 game limit per SD card, but you can use multiple SD cards and switch in/out)
Software that will come in handy:
Sky3DS Diskwriter v1.06b5 + template0310.txt
EaseUS Partition Master v10+ (if your SD locks up, simply delete the partition and delete the MBR and start fresh)
Gateway ROM Patcher v1.1 (for private header IDs)
ROMTOOL v3.1 (for trimming ROMs and improving scroll speed on Sky3DS)
NO BAN NO SKY v2.1 (it kinda works, but not really, better off manually editing template)
Sky Army Knife v1.3 (awesome tool, still needs work)
Gateway Ultra 3.1 pack (so if you have 9.2 or below you can rip ROMS using launcher.dat)
Notepad.exe (for manually editing template)
OPTIMIZER in Diskwriter is nice, but it takes a while to make the backup. Wish there was more options. Like running ROM TOOL to trim without having to backup.
Backup/Restore of EEPROM savedata from Diskwriter works, but Card2 EEPROM=NO still needs help.
Verify is nice, but again, slows down writing time.
It'd be nice to have a menu option to individually make backups of all your game's savedata at once to make reformatting easier.
Making a master backup seems like a waste with OPTIMIZER. Most people already have the collection on disk and can just write the ROMS back in.
Sky Army Knife will be awesome when it starts to combine all these tools into one. Have real hopes for that one.
PokeInjection still works on my firmware, but I currently have no way of ROM dumping and header ripping.
So basically, free games I can't play online.
Otherwise, it's great! I have used it on multiple 3DS handhelds with different firmware, works perfectly.
Can play over network just fine.
Just no ONLINE because of Ban Hammer.
Pokemon OR/AS/X/Y does allow Powersaves to max out $$ etc., just no backing up savedata.
Fits in my 3DS and cartridge carrier.
Wish it was black like the DSTwo. And the sticker... uh... yeah. Transformers. Great. Make a logo, use it. This robot stuff is... yeah.
Oh, and it arrived in the mail all the way from Canada. *glares at GateWay retailers*
If you're trying to decide which to buy, Sky3DS or Gateway, get them both, save yourself the hassle. You need Sky3DS for N3DS to install GW anyhow, and then you can share ROM dumps and savedata with friends over Sky3DS. Don't waste your $$ on ZeldaOOT cart. You don't need it.
If you're under 9.2: Gateway. Over: Sky3DS. Simple as that.