I'm currently using RavenCore. I am also testing a panel of my own, LiquidXanto, but that is on a private server.

We are using cPanel and Direct Admin. Both seem to work great, both have advantages and disavantages. I would say Direct Admin is best bang for its $$$, since the cost is 4 times less than cPanel.

I have cpanel on my personal server, main one anyway but there are others that are good and some for a lot less price.
ServerCP, PLesk, Direct Admin is the other 3 worth mentioning.
Helm for Windows isnt too bad but I dont do alot with it since I have never been one to push Windows servers.
Is all a matter of prefernce I guess.
The one thing I dont like about ServerCP, bout the only thing worth mentioning is that Mod Rewrite isnt packaged in the panel, you have to manually install the mod and try not to break the system which is a bit tricky

Add one more vote to Cpanel,
I use the cpanel's latest version, All our clients demand only that, and it has everything built in it ! The latest version 11 is really rocking, Some months ago We have been using version 10 but now, most of the reselling business are switching over to cpanel 11.
It has an excellent design and great security !

cPanel. Reason - famous control panel for majority customers.

Add one more for cPanel..
I only have experience with one other CP, Plesk, it's a good interface, but when I went to their support forum ... it had nothing compared to cPanel so I ended up finding my own answers.

Support is so important .... even with web host users. The cPanel forum is full of problems .......... hehe ..... and answers. We don't have a large enough business to worry about having to offer other CP's to our members, so for now it's cPanel. I'm hoping that will change

cPanel all the way, has worked wonders and is continuing to do so.

We use cPanel. Ease of use. Compatibility with other host. Easy client transfer.

We use cPanel as its easy to use and our customers love it. We can also provide Plesk, DirectAdmin and Host In A Box.

I tend to code everything on Notepad and them copy it into SSH.

I hate coding in notepad... never liked it

I use cPanel, DirectAdmin and Plesk in the priority order in which I mentioned then

My own server has cpanel but I have Plesk on both Windows and Linux for hosting, cpanel for hosting, lxadmin for hosting, servercp, directadmin as well

LXAdmin is a very nice panel, user friendly and gives you alot of control features over account

Cpanel has become very buggy since new release so in my opinion barely worth the money of licensing any more, but is still most popular among clients cause is what they know

Plesk is decent all around

Direct Admin is kind of limited but a nice panel anyway

ServerCP is nice cheap panel, only thing I dont like about it is is a nightmare to add modrewrite into the config without breaking theor DSM system

we use cpanel, but we are considering to start also using Direct Admin to reduce the costs of hosting to our customers.

cPanel, because it's the most easiest and best around ;]