Hi Anjay,
We made the switch over to Hsphere about a year ago and I can assure you there have been no problems at all.
If customers can use any other CP, they can use hsphere.
Goto our site and click on live demo or online flash tutorials.
I think you will be surprised by how easy it is to use. Combine this with the full functionality (server resource, billing, plan management, payment processing, invoicing, site builders, etc, etc, etc) I dont see how you could go wrong.
Price is right too - 1 time per user fee (around $3-$4 per user, 1 time fee).
If youre looking to design your own CP, the only thing I can think of that I would like to see improved over Hsphere is greater flexibility in the invoicing and improved reporting functionality - ie to track cart abandonement, etc.. , also, a slightly sleeker checkout process with greater modification capability would be nice.
My $0.02