Bought Sonar 2 because it was on sale and had a free update to Sonar 3.
 
I was looking to replace my old Voyetra Sequencer GOLD Plus and Digital Orchestra Pro really wasn't cutting it for me.
I had finally decided to go the Sonar route when I saw it on sale at Sam Ashe and snatched it.

Pro 9 for me.
Jumped to Sonar 1 when it came out.

Beagle
Sonar 4.
 
But it stopped with X2.  I'm not interested in a product distributed by Tascam.

Just out of curiosity...why? It's the same DAW, made by the same programmers and produced by the same company - Cakewalk. The TASCAM distribution simply means more people will have the opportunity to experience and buy Sonar because they have a bigger reach for getting products out into the world. The Cakewalk guys are very happy about it.
 
As to me, I'm a latecomer. I used to bounce projects back and forth between Acid (for looping) and Cubase (for MIDI and hard disk recording). When Sonar came along and did loops, MIDI, and hard disk recording, it sure seemed more convenient.  And then it just kept getting better and better and now we have X3, which I love to use...as a friend and musical co-conspirator of mine who switched from Pro Tools and Cubase said, "it's put the fun back into recording."

I started with version 6, before that AW4416, Alesis ADAT's, Fostex A80, Fostex 4-track.
 
I am now on X1, how things have changed in 20 plus years!

I had Cakewalk Pro 3.0 in late 80's and a midiquest midi card and a Toshica portable computer.
Later I upgrade to Cakewalk Windows 1.0 and 1.25.
 
Ran tape portastudio - using one track as sync track for Cakewalk - and recording and doing bouncing on the three other tracks.
 
Didn't get any further and wanting a 16 track Fostex real-to-real but could not afford it. Lost interest and started my own business and was off recording until early 2000's.
 
Had a couple Fostex 8 n 16 track hdd portastudios and then went computer based. Got Sonar 4 2005 and Sonar 8.5 2009 and now X3.

Just found my Pro Audio 7 cd the other day.  Only skipped a couple of versions over the years.  There were a couple of times I considered sticking with one version (never upgrading again) because at the time I thought Sonar did all I would ever would need it to do  :)  
 
Holy crap was I wrong. 
 
X3c is awesome.
Vernon

I tend to ride the horse I'm on till it drops: I cut my teeth on Pro Audio 9, then went to Sonar 2 and did my 1st CD in that with a 16-bit SBLive card. I remember being wowed by all these virtual tools that would take up rooms of real space in my house if they were hardware...and all for loads less cash, so I was made up.
As my upgrade cycle takes aeons, I was then thus blown away about how vast 6PE was, again thinking, whoooaa..if this kit was analogue, it'd take up half the house.
 Have now of course got gravel-rash on my lower jaw as I gaze like an alien-struck neanderthal at X3...and man, I'll be able to now master within Sonar too rather than in a standalone suite. I'm a chap of simple tastes and I still can't quite come to terms with how much there is for so little outlay in this DAW(though of course am knocked into reality by getting the OS and sytem to run it, but yet again that was ever the case).
Phew, heads here far more seasoned than mine who ran with 486s, way to go guys..!

I also started with Cakewalk v1.0 on a 3.5" floppy, Packard Bell 486 SX, Win 3.1, Sound Blaster and a seperate midi card, Roland D-50, Tascam 4 track cassette, Roland R-5 Drum machine (with "Human Feel"  ) later I bought a DAL full duplex audio card,  and so on and aon and on and on
 
It really is astonishing, when you go back and look at it, how far we've come. with VSTs and Kontakt and X3 and multiple Gigabytes of RAM...etc

jscomposer
I paid $400 for Cakewalk Pro 3.0 in 1992, along with $2000 for my 486SX! My friends were in envy over the 2MB (yes, megabytes) RAM and the mammoth 120MB hard drive!! My controller was an Ensoniq ASR 16 sampler...still have it but the disc drive is toast.

This reminds me of a conversation I had with one of they guys in a band I was in back in 1982. The subject of computers came up and he was in awe that some computer somewhere in California had two megabytes of RAM. To be honest, so was I.

Since v1.x on floppy disk media, bought it from Greg Hendershot over the phone back in the day when he was doing it all ... :-)

For me, it is less about loyalty, and more about the lack of free time to indulge in my hobby. There are quite a few good DAWs out there. I know this tool pretty well, so I can make music in what little time I have. It's nice not having waste time spinning up, it's also nice being able to pull up half finished projects from years ago. Although Waves kind of mucked that up when they dropped DX in favor of VST.