Worst area is the Austin cooridor. Yes, it has it's "flavor", but I don't know anyone who actually likes it.
If property values go up in Oak Park, it's all the same %'s in all areas.
In Oak Park, there is NO area that holds value better than the other, unless something unusual will happen that will force your property to decline (i.e. building a McDonald's at the end of your block). If someone tries to sell you on that, they do so because they either believe you're daft or are daft themselves.
Don't count on values to increase anytime soon as property taxes are through the roof, homeowner exemptions are currently phased out and Oak Park is due for re-assessment in 2014 :D. That's all in light of increase in local crime. So, basic supply and demand law tells you, property values will actually decline in the next few months.
Good things about Oak Park: Schools are great. That's just a fact. Park district offers a lot, including nice parks, activities, however you will often find that certain facilities are hogged by non-Oak Parkers which pisses taxpayers off and Park District doesn't seem to care or do anythign about it.
Restaurants are.. meahhh.. ok. Forest Park offers more. Close proximity to Down Town via Blue or Green line is a huge bonus. The Village also offers some incentives for first time homeowners, business owners and some other odds and ends that are worth checking into prior to buying a home.
All in all, Oak Park is great only if you have kids and work down town or in the area. If not, it's really not worth investing into and mainly due to unreasonable real estate tax assessments. You will get more bang for your buck in River Forest or Forest Park depending on your situation.
(I just viewed a $400K home for sale here on Trulia with $18,000 annual Real Estate tax. That's almost 5%!!! Are you ready for that?)