Sygic might be a nice SW, the price would be interesting ...
However, given the uncertainty on the availability (and quality) of Ovi Maps (They seem to skip Maemo 5 ... likely)I would not recommend to spend much money on Sygic or any other Maemo 5 SW. It sounds as if M5 and M6 will be as incompatible as previously, and no upgrade paths - well, of course you can buy another Nokia in half a year ;-)