I have a door sized N scale layout made with Unitrack. I had very good luck with it, and would use it again. As far as sectional track goes, Kato is pretty much the top of the line. Great fit, no problems with electrical, decent selection of radii. Of several hundred sections, I did have two that had misaligned rails, but I had extras, so it didn't matter. I wound up using the two bad sections for practicing ballasting, etc. Downsides to Unitrack, some of which are the same with any sectional track are:
1. The roadbed color varies from lot to lot, so you can end up with light and dark roadbed pieces next to each other. Not a problem if you are ballasting or painting the track anyway.
2. Pricey compared to other sectional track.
3. Also an issue with any track you choose - when handling, be careful not to let already connected sections bend vertically at the rail joiners, or the joiners can deform and loosen the connection. This could allow vertically misaligned rails. I had to file/dremmel a few joints that I had mis-handled in this manner.
4. I didn't care, but some will note the not realistic look of the roadbed and tie spacing. I guess it's more like Japanese tie spacing. I think it's not an issue.
5. Although there are lots of different radii available for Unitrack, there are no curved turnouts. Plus the curved sections are available in multiples of 15 degrees. So, it's hard to make those really pretty long, flowing curves you can get with flexible track. This is another issue you have with any sectional track.
Overall, for a smaller layout where the extra cost isn't such a big deal, I highly recommend it. It would be a pretty big investment for a really large layout.
Hope that helps a little.
Mike