RagManX: It depends on how the charger is designed. If it's slow and takes overnight to fully charge the cells, then it will work, but you may have to wait longer for full charge because most NiMHs have higher capacities, as much as 2-3 times that of nicads (1200-1500 mA-H verses 500-1000 for nicads). A fast charger for nicads may overcharge NiMHs because NiMHs don't heat up as quickly, and when they reach full charge their voltage doesn't drop the way nicad voltage does.
Temperature isn't a bad way to detect full charge, and if cells feel warm, they're about charged.