Its common sightseeing for me to see wordpress permalink untouch or customized.
In my opinion permalink provided by wordpress really help in the eye of search engine.
For demonstration purpose I take a few blog from Wongkito Community :
>> Default
1st example : Take IT Or Leave IT
When I click the title, I’ll see this url :
http://blog.jafisnet.com/?p=200
As you see posting url use number . (/?p=200)
>> Custom
2nd example : Amarok aja deh
When I click on the title I saw this url :
http://blog.ibunk.or.id/index.php/2008/06/26/amarok-aja-deh.ibunk
Posting url have components : index.php, year, month, posting title and .ibunk
Those url use wordpress permanent link feature which is accessible from here :
1. Click ‘Settings’ link.
2. Click Permalinks
3. Common settings will list a few options
Just click on ‘radio button’ to activate your option.
To produce url in the format that I use in my family blog :
http://keluarga.rasyid.net/2008/06/25/dari-simpati-ke-kartu-halo.html
what I have to type in ‘Custom Structure’ field is :
/%year%/%monthnum%/%day%/%postname%.html
Click button “Save Changes’ to apply.
P.S :
Permalink will make your transition from blogspot to wordpress conversion easier and make sure your existing post in search engine left as is 
More reading for complete reference in wordpress permalink click here.
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