Similar results here, although I haven't tried batteries, just mains power. Using the wire antenna, anywhere in the house is fine. I can put one in my shed out back (100 ft or so) and it seems to work fine too, I should check the RSS on it.Chip antennas will definitely not go as far in the house, haven't tried them outside but I can find locations that aren't reliable. Also have a couple with the RPSMA connector, but haven't done much with them.
I have an application that transmits data once per minute, and I chart the RSSI. I've seen it occasionally as low as -90dBm, maybe even a couple less.
Interesting that during the night when the house is quiet (electrically as well as otherwise), signal strength is stronger and very consistent. When I'm in my office where the one node is, with two or three PCs running, and lots of fluorescent lights with electronic ballasts, things bounce around much more.
The other interesting thing (I'm using S2 XBees) is adding a third node physically somewhere between the other two. This will sometimes cause an increase in signal strength because the traffic will sometimes switch to be routed through the intermediate node. So that's one way that the mesh networking can be seen doing its thing The RSSI for the intermediate and the furthest nodes will then be nearly identical -- RSSI only reports the last hop.
I've got the higher powered ones series 1. Nearly a mile outside, half mile thru trees, with tiny rubber antenna. Measuring packet retries after changing the max retry parameter to a higher number is a better indicator than RSSI. Even when 100% get thru, you can measure the % retries before they are successful. It was difficult for me to figure out, but now it is easy to put them to sleep even for a short period of time to save power using a hardware pin between packets.
I tried the highest value, I don't recall what it is. But that is not much better as an indicator than 3. Look at the change in total retries.