Similar to cash machines in the Philippines, the usual ATM's in Indonesia have small cash withdrawal limits per transaction, and as my bank gigs me pretty hard for each foreign ATM withdrawal, this can be a big pain in the ass. I've seen ATM's with limits as small as 600,000 rupiah, which is like 60 USD. I'd say a good number to shoot for is 1.25 mill. rupiah. And of course 99% of ATM's I've seen in Indonesia give you 50,000 rupiah notes, so you're always walking around with a huge BRICK of 5 dollar bills in your pocket (good luck if you use a wallet!).

But in Jakarta, there are several BCA (bank name) ATM's that spit out both 100K notes and will allow 2.5 mill. per transaction, something, IMO, that makes them well worth looking for. Not all BCA ATM's do this, but if staying in Kota, there is a BCA branch on Mangga Besar about halfway between the Mercure Rekso and Lokasari Plaza, on the same side as Lokasari and across the street and to the left from Sparks hotel. Beware, though, that this ATM is not open 24 hours.

Also, HM pointed out CITIBANK ATMS at the Manga Dua Mall that gave out 3mill rupias in 100s.

There are usually money changers at the Malls (i.e. 3rd fl Atrium Mall) that were not picky about exchanging 100s and gave decent rates.

At Lokasari Plaza, I got 3,000,000 rp from the HSBC machine. I should have cancelled and tried for more, but at present that seems to be the best bet for maximizing your withdrawals.