In Local 58 here. There are good and bad points. I'm on the construction side so it may not apply to you.
Good: wages, benefits, tool list, everything is spelled out in the contract. Training is the best you can get...not even close otherwise. You should be able to travel the country if you want (and need) to with not many problems.
Bad: they can't conjure work, and in many ways don't "sell" themselves well enough (keeping on local/state governments to enforce code and regulations) thereby opening things up to the competition to undercut with shoddy (and sometimes illegal) labor and shoddy materials.
Worse: the International part of the IBEW is run by a bunch of slimeballs who consort with the contractors they should be working with (or standing up to) and do their best to keep their positions and wages while most of those who do the work struggle. We finally managed to vote out some of the slime in our local, hoping they can start to enforce some of the internal regulations that are designed to help the brotherhood.
I've been laid off for a year and am just now back to being eligible to go back to work...and at this point I won't be until next year (that being my choice though for financial/family reasons at the moment -- and yes, long ago removed myself from unemployment despite still having credits).
As for the concept of unions in general...anyone who says they want to bar workers from joining together and selling what they can offer (labor) better firmly back the abolition of corporations and investors being able to band together and utilize what they can offer (capital) in the same manner.