I have used Bird Recorder (produced by Wildlife Computing) from an early stage, and upgraded to Wildlife Recorder when it became available. I have always found it to be very user-friendly and good value for money. Upgrades and patches are released on a regular basis, available through the website (free with a support arrangement), as are updates to species files. This is always very useful with so many changes to taxonomy nowadays. You can also set up lists for mammals, butterflies, dragonflies, plants - species databases for these are provided with some versions of the software.
I also use Pocket Bird Recorder, which means I can keep my trip lists on my PDA and then upload them to my laptop when I get home.
There is a lot more I could say about the product's versatility but I also find the product's developers very open to suggestions for improvement. I've only made one suggestion but it was incorporated into the next upgrade.
Hope this helps.