First thing to be aware of is that this is Leopard only.
After the usual install/upgrade malarky, the program is ready to go.
The first thing you notice is that the program has integrated with your Address Book and your iCal. If you've got a lot of info in these programs probably best to back them up first, as any changes you make in Bento will reflect in your actual data. You can also import your e-mail from Apple Mail, but this is one way only. I found the Address book feature quite useful as I've never got round to adding my data into Address book as its too fiddly and US centric.
The front end is very reminiscent of old school Mac, and as I've used Filemaker before (and liked it) it's all very familiar.
However despite it being very easy to add data to Bento, there are some obvious limitations. One of the obvious things to do with your address data is to print out address labels with it, but Bento doesn't support this! Very odd, so it's of some use if you manage large collections or a membership list, but I don't think that Filemaker have really thought this through.
At the moment I would recommend the 30 day free trial if you're interested, and see how you get on but with the limited printing options it's hardly essential at the moment.