Hi,

I want to know about modernbill, is it good for web hosting company? is it simple?
is working with paypal as merchant good? are they serving good?

Well, many companies are using them. It works fine for some and helpless for some. You can find the reviews on WHT -

http://www.webhostingtalk.com/showthread.php?t=215658

ModernBill is a platform that a lot of Web hosts use.

I wouldn't say it is necessarily the "simplest" system to use. If anything, it can be a more complex system to setup sometimes but that is due in part to the fact that it can also be a very flexible system that is very extensible.

In my opinion, PayPal can be a good secondary payment option to include - most Web hosts these days also have a direct merchant account that they use for a lot of their payments. It can't hurt to have PayPal, though. Giving your customers choice is always a good thing.