What's the situation with the 'ř' in Czech (R hacek)?

I'm a learner of Czech myself and I also find it hard to pronounce that letter. I'm in the Czech Republic right now and my teacher, who is Czech, taught us, that for example in the word 'tři' (three) it is often pronounced as 'tchi'. She told us that even many Czechs have problems pronouncing the ř sound. As a rule, if it is in the middle of the word you can get around it by simply saying 'ch' and do that very fast. It works, trust me;-)