I like that it keeps the same feeling of the Foursquare application and website (although naturally that might cause some issues down the line) but right now this seriously depresses the learning curve. Switching to this client shouldn't scare any users.
It also has the potential bonus of running in a larger font with bigger buttons than the official client. And when you're out and about, having to stop so you can aim at a very small touchscreen button gives you yet another reason to not check-in. Anything which makes checking-in faster with less friction is a good thing for a geo-location service.
As always with anything labelled alpha, it could crash, not everything is fully tested, and it's only polite to provide feedback (good and bad) to the author once you start using it. Oh and Neli? It's Finnish for "four". Obviously.
More info at Substance of Code, download the alpha via Forum Nokia.