The day your competitors start copying you, it means you struck a nerve and are heading in the right direction.
The trick here (which is hard to do, unfortunately) is to make sure your product has a set of features that are hard to replicate. It's not the design, layout or navigation... it's what's under the hood that really matters. The algorithms you use, for example.
But going back to your base question: you SHOULD offer customers the ability to try the product for free, online.
If customers can use you solution for a period of time, you'll have them evaluate it in self-service mode. This will bring down your cost of sales (instead of having to schedule demos, conf calls and send your sales squad to meet the customer). They'll do a hands on evaluation of the product, and compare it with other alternatives they might be looking for (some may not be available for trial).
At the end of the day, you might loose 90% of all trial users, but the 10% you convert into paying customers will have costed you virtually 0$.
So focus all your energy in:
1) making your product non easily replicable,
2) providing a good trial version, with easy sign-up and instant gratification (a WOW every 5 minutes since the prospect signs-up)
3) getting as many people as possible into your site and onto the trial (remember, this is a numbers game. For example 1000 people visit, 5% sign-up, 10% become customers - 5 new customers for every 1000 visits). Increase the visits, and grow your customer base)