I have a request from client to base their business on Plesk control panel. Anyone here used Plesk? How much is it different from cPanel in terms of ease of management and features? Is it easy to install?

In genereal: Plesk is somewhat easier than cPanel. So it's fairly easy to manage your server with Plesk. Did you check out the demo? http://www.swsoft.com/en/products/plesk/demo

It expected you to know what you're doing regarding server management, the client-side featires are equivalent to cpanel, but the admin-side options are far less than WHM.

Apart from adding Clients so they can add their domains we just use SSH for everything on our Plesk and Virtuozzo systems.

I personally didn't like Plesk much at all. Cpanel has been my favourite and always will be

I don't hate Plesk either, and if I couldn't get Cpanel, I'd use Plesk next. It is simple to use, but I'm not sure what it lacks. There is just something it lacks, mabye it's just the feel or I could be very used to Cpanel now, since I've used it for around 3-4 yrs.

its not something plesk lacks but its actual softtware pleskk is a little complicated while cpanel is alot more basic for example plesk my first time on it i was there for about a hour setting up nameservers ect but cpanel i did it within 2 minutes