I've been selling on eBay for a little while so I may be able to offer some help.
Non store holders can list 30 things a month with no listing fee, then its about $1+ ea. With a store its 20c for buy it now or 50c for an auction. You will still be charged a final value fee based on ur selling price with or without a store. When you're starting out you may only be listing 20 - 50 things/month, so this can be handy.
Pictures are now free for everyone. Store or no store.
A lot of the special features have been removed, such as featured listing and appearing on the home page.
As far as I can see all these recent changes make it easier for small or new sellers to compete, especially while we're trying to find our feet in the first few months. I sold without a store for about 5 months before I found a good product that gave me enough sales to justify it.
I would suggest you sell for 2 - 3 months without a store, then re-visit it.
Oh and feedback's feedback! Discerning buyers will be able to see how much of your feedback is for buying, but many just look at your score. As you can only receive positive feedback for buying its a good way to get a high score with 100%. I was maybe a little bit cheeky and bought 50 VERY CHEAP things in a short period to boost my feedback score. Sales went right up ;)