Yep!! I was there 4 years ago and really liked it.
Warsaw is worthy of one night and a quick zip around town but if you don't make it, no need to shed tears.
I spent some time up north at Gdansk (a good base for the north), Sopot (coastal resort), Gdynia and Malbork (castle). Train connection is great up here in between towns. Lots of amber jewelry if you are into that kind of thing.
In the south, I went to Wroclaw, Krakow (UNESCO historical site- definitely worth a visit), Oswiecim/Auschwitz-Birkenau (infamous concentration camp) and Wieliczka (UNESCO salt mine).
Other musts are experiencing a milk bar (cheap food for the locals... you know you are in a good one when nothing is in English) and vodka of course!!
It wasn't expensive four years ago and I was on a backpacker's budget.
Go for it!