I'm in the same position as the OP: I ride a hardtail MTB with semi-slicks & cheapo stock flat pedals. I've been in the market for a harder-sole cycling shoe, and last night ordered the Diadora Toluca from Nashbar. Killer sale price, looks like enough tread to work on flat pedals, available in my size (13 US,47 EU). Looking forward to trying them out.