The subject says most of it:
I like Linux because although there is a GUI, it just sits on top of the command line but the command line really runs the show.
Linux doesn't try to hide things from its administrator (root) like Windows does. There's no "registry" that runs the show but can only be accessed by a program that runs inside the GUI.
Linux is logical. Ok, you have to be able to think a bit, and I sure as heck have had to come running to you folks for assistance on many occasions, but the solutions are logical and make sense once learned.
Linux is stable. I have managed to crash programs, but never the OS... and I crash Windows regularly at work. <MUTTER> damned windroid nazi sysadmin </MUTTER>
Linux offers options, you can surf the 'net (some of it anyway) with Lynx or with a graphical browser. You have multiple options of spreadsheeting, databasing, word processing and other applications and are not tied to a single program or suite.
Linux does what I tell it to, and not what some clowns in Redmond tell it to do. I like that a lot.
Linux is secure. The data on my computers is mine and with Linux I'm fairly confident that it will stay that way.
Linux doesn't make me a thief for putting an OS that I purchased (yeah, I buy it) on more than one of my computers... or even on my daughters' computers, or those of my students. I may feel like a cheapskate, but not like a thief.
I feel more like I'm in control of my computer and its data than I am when on a WIndows computer. Oh, OK, I still drive with a standard transmission. Maybe I'm a control freak... or just damned old.
These are just a few of the reasons I like Linux. There are more, but I'm in the upstairs computer room, and the fridge here is empty, so I'm gonna knock off here for now and get me another few bottles of liquid inspiration (aka beer).