Lazarus is Free Software, which is awesome, and its feature set is also mature and impressive (I wouldn't have thought that the project also has a 20+ year history already).
I do recommend it highly if you can't get your hands on Delphi, don't want to support Embarcadero's antics, or work with an open-source project anyway. Several major component developers, including the great guys at TMS with their cloud pack and Raspberry Pi components [0] make a ton of awesome components that are available for both Delphi and Lazarus and I can highly recommend them.
If you're operating in the commercial space and have a budget, a bigger team, strong network, database or certain other commercial requirements, you might appreciate the support options and greater choice of 3rd party components which can be installed in Delphi with just a click and that save just so, so much time in getting your product to market.
If you're learning or teaching the language, working in a small team or alone, or require a feature set fully supported by Lazarus or just like free software, I wholeheartedly recommend Lazarus as a great alternative indeed. If you're somehow in the middle, check out the Delphi Community Edition too and just find out what suits you better. I guess it also comes down to what you're used to...