So, is it happening where you are, especially in states new to ALDI?  Save-A-Lot is down to one California location in Coalinga, over a hundred miles away from the nearest ALDI in Bakersfield.  Save-A-Lot stores in L.A., Riverside and San Bernardino counties didn't fare so well and began dropping like flies within weeks of ALDI opening.  When you read Yelp reviews for ALDI in California, many positive reviews are from transplanted out-of-staters happy to see a familiar name.  Perhaps Save-A-Lot was only a stop gap until the "real" thing arrived.

Grocery Outlet, of course, is a whole different animal specializing in deeply discounted short-dated non-perishable national brands but they also sell dairy, fresh meat and produce at market price to save you a trip.  According to many sources, they and ALDI opened more new stores in California than any other grocer.

Still waiting for Aldi here in the Bay Area.  I suppose finding cheap locations is delaying the process. 

I think when Aldi does show up, I'll not shop there regularly.  Like Sprouts and TJ's, I'll probably go there for specific items but still do most of my grocery shopping at the big supermarket chains.

. . . that Grocery Outlet began life, according to their History page, in the generally more affluent northern end of The Golden State and is gradually moving southward as well as leap-frogging the country as far eastward as Pennsylvania?

Next up is Lidl which seems to be in a permanent "any day now" status.  Plenty of news that they're going to open their first stores in Virginia but no one knows when, hedging their bets with "this summer".

I haven't been to Grocery Outlet in years.  I found too much bad-for-you stuff there.  Maybe they've changed their merchandising and are worth another look.  They've been around for so long that they were likely able to negotiate favorable long term leases in left-for-dead strip malls, which is where the majority of their stores in this region can be found.

In the Eagle Rock area of L.A. near my sister's house, a new type of small footprint Target is going in where Fresh & Easy used to be.  The neighborhood association is pushing Target to focus on groceries, but since margins are low in the grocery biz, they're going to have to accept some of the more familiar Target merchandising as part of the deal.  I can't imagine where Target would put such a store in my neck of the woods, but I've heard there's already one out by Apple HQ.  A small Safeway took over the space previously occupied by a F&E store near me.