I've been working on one of my aStores : The Flashman Papers & Other Military-Historical Fiction (US). I like to have a long series of novels on the go, almost always military-historical fiction set in the C18th and C19th. I've read Flashman, Aubrey-Maturin and Sharpe and I'm two-thirds of the way through Hornblower. Now I'm considering what to read next and decided to add some of the possibilities to the aStore.
I've been an Amazon Associate for many years and used to have a script running on the sites to recreate a store using the Associate links. It worked really well (particularly with Google results) but it used bandwidth like you wouldn't believe! aStores are so much better; Amazon handles all the tech work and you just have to set it up and link to the store. The only real restriction is that visitors can't search off-topic, as they could with the old script. I've suffered a bit from that, payments-wise, but make up for it in the significantly reduced hosting costs. Payments aren't that big anyway; you only get a few pence per sale but, taken as Amazon gift certificates, it's nice to have a "free" gift from Amazon each month.
I haven't tried really intergrating an aStore with a site yet; generally I just link to the store off-site but I do use iframes at Mandy's Book & More Store. I would like to have a go and set a store up in that way but, for my sites, basic aStores are working out well.