I basically buy everything Fed related. I don't buy much KDF stuff, as I only have 1 KDF character and seldom play him. Since I tend to earn anywhere from 2,500 to 3,500 free Zen per month, and I also receive a 500 Zen Stipend, I get most of the items I want from the C-Store for free. There's not much reason to not buy something when it's free.
I like costumes, more options for tailor and up until the season 1 TNG uniforms I owned every costume in the store but I didn't buy it as there was nothing in it for my KDF characters.
I also used to love getting new ships but again since I play mostly KDF now the recent ships I didn't buy as I have no interest in the having more Fed ships when I rarely play Fed besides dilithium farming, helping in an STF or doff recruiting to sell to fund my KDF alts (which thanks to the fleet doff mess up is probably gonna hurt my ec balance a bit).
If Cryptic want more of my money that's how they'll get it and since I have most KDF items in the c-store unlocked that could be a while before I buy more C-Points. I'm not even getting more during the 15% promo running... nothing much to spend it on.
Bottom line, what interests me is more goodies for the KDF and that's what I want to spend my money on.
Man is a gaming animal. He must always be trying to get the better in something or other.
I did not buy anything ingame just yet (haven't started playing due to the holidays) but i did get me the Digital Deluxe and CE editions though!
And took "advantage" of the extra Zen offer a few days ago and got me some currency to spend on something nice along the lines!
B.t.w. got me a test character (to see if i liked the game) that has gotten some really nice items, DOFF's and more which i will transfer to my "official" character whenever i get a chance to start the game!
Bought the Atrox Carrier about a week ago, then just recently bought the stalker fighter (dang thing is freaking awesome when using Plasma HYT...and sitting right on top of an enemy and letting one loose lol)
only thing i dont like about the store is getting tribbles...seeing as its a ONE TIME purchase...so if you accidentally discard one you are SoL until you have millions of EC -.-....
but i love the fact that all the c-store ships are account bound.