I ran some 27 inch wheels with 630:25 Panaracer tri-sports for 4000 km (fixed) and loved them... they got replaced with some more period correct wheels and tyres (700:25;s) on high flange hubs.
I just gave the old wheels and tyres to a friend who was building up a fixed gear on an old Apollo frame that needs 27's, the Suzue hubs are to die for and the Ukai hubs make for a really strong and fast rolling wheel and his initial report was that he loves these wheels.
The only issue with 27 inch / 630 wheels is the availability of rubber.