My wife and I are looking in the Wildwood and Grandwood areas of Gurnee. During our first bid on a house we offered a VERY low-ball bid of 135K (with my realtors "go for it" consent) to their 189K asking price. Once it was in, our realtor handed me a report showing the recent sales in that area. I sat down with my trusty calculator and worked out the averaged differences between original asking price and closing price on 13 homes (included 1 foreclosure and 1 short sale) in that area. Similar to Tom Martinson's answer the closing prices ranged from 13.4% to 33% below original asking prices...and the the average was 13.9%. I also ran the math without the foreclosure and short sale in the mix and came out essentially with the same percent discount.
So I agree with Tom's assesment, although I am still going to offer what I feel is reasonably lower to get the best deal I can....It's our money...not the realtor's. You can always raise your bid to whatever you want as long as you stick to what you can afford. You can always put a time limit on an offer...say 12 - 24 hours...and they can always say NO...and risk not selling.
In the end our 1st offer on the house (29% lower than asking) got denied so we added 10k and that got denied...then another 10k with a request that we wanted them to reply with a counter offer. They countered a 9k discount and we walked away. We also found out the buyers did NOT "need" to sell, they had another house in Nevada.
My suggestions to your are to search each house address on websites like http://www.trulia.com
(paid service with GOD info...even shows bank/lender name) to learn its sales history and other public record info. Ask your realtor to talk to the listing realtor to find out if ANY other offers have been made, for how much, and if any deals fell through. After your first visit, go back in the house WITH THE TENANTS AT HOME and just casually ask OPEN ENDED QUESTIONS like, "so are you moving out of state? Also, ask, "If you were to buy this house today, what would you need to do to it? Have them tell you stuff...ya they'll boast but you can find out a lot of info if you know how to ask questions the 'right way'.
The main problem is that sellers are trying to keep the price to not lose on the deal, and we are trying to buy at a good (if not low) price. Good luck.