just going to ask the same thing as accordionman---
MAS90 is great for low user/volume--with the exception of reporting speed via Crystal Reports (much slower in MAS90). MAS200 is much better for the higher volume/user count.
And MAS90 is pretty good straight out of the box--very easy to navigate/user friendly. The "modules" that you pick for your specific system should be hashed out with a good MAS90 reseller/support person. Hopefully there's one where you are, because they'll help tremendously (though, they are sales people, so keep that in mind). But the common backbone modules included and/or added on:
L/M: Library Master
G/L: General Ledger
A/R: Accounts Receivable
S/O: Sales Order
A/P: Accounts Payable
I/M: Inventory Management
P/O: Purchase Order
And Crystal Reports is included I believe.
e-commerce, RMA and Payroll are other common modules.
If you can deduce (generally) what you're doing in your current accounting system relative to the MAS90 modules and then what's missing before you meet with a Sage Reseller/Support, you'll really get a lot out of their pitch. It's also good to figure this out to get a general idea of how migration would work--which could be a huge problem--or pretty slick. Also, aside from the base modules, almost all can be added on later--if you find the use for them.
There are a couple issues that are also important--server platform being one. They really pushed towards Windows Servers, but Netware is supported (for MAS90). I think they're discontinuing the support for unix based (solarius) systems. There are rumors they'll release a Linux-ok version but I'm not sure (and MAS200 is SQL based).