Hi, First, I see (posts on this mailing list) that OO ideas are well known in functional community :)
So my questions for you all are:
* Is it really worthwhile for me to learn OO-programming?
Learn or not to learn? I would say: yes! There is whole new universe to discover: UML, design patterns, classes and objects, data structures based on 'pointers' (and you can modify them, surprise!) and of course many algorithms that work on this structures (please note, that many books about algorithms and data structures take imperative approach), OO databases, many many many libraries for almost any thing! and finally, you will be able to try stable, well known and widely used tools (think about GUIs, game engines, embedded systems, mobile devices and all this fascinating stuff you can do with them).
* If so, where should I start? There are plenty of "functional programming for OO programmers" but I have never seen "OO programming for functional programmers".
Get a book (big and heavy!), forget all about programming and read it with fresh mind. Do _all_ exercises from that book.
* Is it true that learning other programming languages leads to a better use of your favorite programming language?
I would say, any know knowledge has impact on your life. Programming skills also.
* Will I learn new programming strategies that I can use back in the Haskell world?
Here I can't say much, I'm just starting with Haskell, but if you would go with C++, then you will also learn some C by the way, FFI is waiting..
Thanks in advance for your kind responses,
I hope it was helpful. Emanuel