Does using third party controls like DevExpress in windows forms, wpf, etc increases/decreases processing time and memory consumption ?
They surely do increase ease of development.
Their support online is also limited, unlike the native controls which Microsoft provides.
Is using them worth the cost ?
You're basically getting a development team extension for four figures (or less) a year, so yes it's worth the cost.
Their controls performs well, CPU and memory wise, they're easy to use and they look good too. Users loves working with them. Plus, their productivity tools are top of the line.
The ONE thing you'd want to be careful about is their position on exception handling. DevExpress doesn't believe in fail-fast development and sometimes they will hide exceptions - yes, even those your code produces - to "help" you making your app "stable". Unfortunately (and expectedly), it creates much more problems than it solves.
This is the ONE BIG issue I have with them. If it wasn't for this I'd say it's the best 3rd party control makers around. By a long shot.
Just consider the time alone you will spend on creating a custom control and making it work, that has already been created by n vendor like DevExpress, saves you money.
When it comes to the controls them self it all depend on your needs. I found DevExpress exceptionally good. The ease of working with the controls are better then it's competitor, but then again, a well polished Dev with say C1 controls, would disagree.
When it come to report designers, C1 is extremely slow. Devexpress's designer in WPF is not so good. Very buggy. Infragistics reports can be build cross platform, so that is n a MUST have.
It all boils down to your specific need. If you have the money available, then it will be a good investment in the long run.
I use them at work and would wholeheartedly recommend them. In response to some of your issues:
I'd personally chose them if you have the money available.
I also use DevExpress's VCL at work. I'm quite satisfied with the entire experience in learning and using them. I would re-iterate what the other posts said. I would also add that DevExpress has plenty of trial periods where you can try out their entire offering, or you can request a trial of a specific package if you know what you're looking for.
I was using componentart before, but when I used Devexpress ,then i thought that worths , you can do everything easly and quickly.
In terms of quality, feature, ease of use and support, I'd say yes.
But there are huge annoyances in term of license. One license is one seat. build server is grey zone, and when people in your team needs to join in, it becomes a sudden unexpected expense, usually this happens after 1 year thus you got to repurchase also your own license (because of 1 year limit combined with versions update and you can't buy old versions).
