Do you use them?
 
Why and when do you use them?
 
How do you use Cakewalk with arpeggiators?
 
Do you sync waves or do you use instruments to create them?
 
 

Occasionally. By "occasionally" I mean 1984.

I use arpeggiators quite a bit.

Why? Because they're there, they're a component part of some of my synths, they're a big part of what defines electronic music. And because sometimes just running an arp and a few modulation sources then hitting a bunch of notes turns up something interesting.

Mind you, I'm old fashioned enough to use hardware synths and sequencers as well as DAWs and plugins. Or maybe modern enough, voltage-controlled analogue gear is doing very well for itself at the moment.

As for how I use them in Sonar, it's the same as I use them in Logic or any other situation. Hook the synth up for MIDI and audio, sync the MIDI to the DAW using MIDI clock, mess about, apply a few effects maybe and record the results. Then keep the bits I think fit what I'm doing at the time, delete the bits I really don't like and store some of the rest in case it comes in useful sometime.

i don't use them and i make electronic music.  I feel they are too limiting.  I like to control where each note goes using the PRV.   

I use the arp built into Omnisphere quite a bit in my music, but there again the arp is very flexiable. It now includes limited step sequencing, which is okay when I need something simple otherwise I turn to my Schrittmacher.

I use arpeggios/arpeggiators.
 
Sometimes, I will use a midi sequence and sometimes an instrument sound with a built in one note sequence timing.
 
Arpeggios add specific texture to places, they are the polyphony of the chordal homophony, they augment and inspire melody.  
 
If a section sounds bare I will try an arpeggio, if the arpeggio distracts from what should be a silence or concentration on other elements, then I will remove it.
 
I like midi arps, sample arps and instrument arps.
 
I instinctively gravitate to what type of arpeggio I need, dependent on the parameters of my instruments and the song vision of how I want it to sound like.
 
Arpeggios can reveal hidden rhythms, signature melodies and themes of the project.
 
A song is a balance between sound and silence and arpeggios are a good way to create sound.

I like arps and use them in many of my tracks. Like some of the others above, I tend to mostly use the arps that are built into my hardware and software synths, or I still use good ol Catanya on occasion.  I've never been a big fan of the ones built into Sonar, particularly not the ones that aren't actually arps (i.e., the MIDI sequences) and I"m not a big fan of step sequencers.  I rarely use arps in a static fashion, either, just to cycle through chord notes.  Instead, I often use a combination of chord and melody or countermelody and have the arp cycle through all of the notes to add interest.
 
I particularly like arps like the one in my Virus TI2, Omnisphere, Blue2, Catanya, etc. that allow me to create my own rhythms, rather than straight note divisions, especially if they have a groove/swing parameters.  Sometimes, a straight 8th or 16th note repeating pattern fits the part perfectly, but more often than not, I want more rhythmic variety in my arps.

I rarely use arps unless I come across a patch in a synth that I really like the sound of.

I prefer to use a sequencer. Reaktor 6 has some great sequencer blocks. I also have a Metropolis sequencer in my modular synth.

As for the "why," I generally prefer to have more than just an arp sequence going on...

biodiode
I use the arp built into Omnisphere quite a bit in my music, but there again the arp is very flexiable. It now includes limited step sequencing, which is okay when I need something simple otherwise I turn to my Schrittmacher.

I've played around with Sonar's arp a few times, but never really used it.  Omnisphere's I've always used, and since ver. 2 came out with the ability to change note increments it's become an amazing creative tool in itself. 
 
Oh, and to bitflipper,  I didn't give up on arps until '86. 

I think what most people don't take advantage of with Sonar's arpeggiator is that you can bounce the MIDI notes it creates to a MIDI clip and then edit the notes individually. I don't use basic arpeggiator presets (up/down etc) unless it's that sort of 80's electro bass kind of thing I'm looking for, but what I find great about bouncing the Sonar arp notes to MIDI is that when you roll your sleeves up and get to work on the notes in the piano roll, you can turn a basic arp pattern into something totally unique. Delete the odd note, add a few of your own, move a few others around, and you can come up with some amazing lines. This is especially true if you feed the arpeggiator some complex jazz chords that you'd ordinarily be stuck for ideas to write lines over. I've ended up with some almost Coltrane-esque type lines by doing this. The arp notes give you a good starting point by laying out the tones of the chords in front of you, then you shape them into something more interesting. Give it a try. 
 
I have to say though, Cthulhu is superb. The arpeggiator is really fantastic and can be tweaked to do almost anything. It's miles ahead of the Sonar one (and you can record the MIDI to a track for editing as well).