Do you like Cisco Modular Routers29XX, 39XX? why? what is configuration complication compared to other routers?

Basically depends on the requirement. If you have requirement to use serial interface / ATM interface / E1 Interface then modular would be good choice. Or if your requirement is to use just a couple of FastEthernet interfaces then why use modular? Working on29xx or39xx both are same for me, I like working on Cisco.

I like the29xx and39xx series routers, its very easy to configure if you have the proper knowledge in configuring it. Eg. for configuring leased lines, it will take maybe5 to10 mins. 

It depends on the requirement...