I'm down to the last few bosses in Crackdown and starting to focus more on hunting the orbs.  In general I really enjoy mechanics like this, where exploring the city is a key element of the game.  The appeal of just being "in" the city is a lot of why I like open ended city games, so having that be in alignment with my game goals is always pleasant.  But I think that Crackdown may have gone a bit too far.  Between the two types of collectibles in the world, there are 800 (!) orbs to collect.  300 of which are intentionally hidden in obscure and hard to find places.

Now, I don't mind a bit of collection.  But I do think if you are going to have it to that level, it is incumbent upon the design to provide some balancing mechanism so that the last 20% of orbs aren't going to be a nightmare.  Normally with a "reasonable" number of things to collect like the 50 horseshoes from San Andreas or the CDs from Saints Row, it is feasible to use a strategy guide or FAQ to track down the last few.  But with 300 (even setting aside the 500 agility orbs) that's a much harder problem to manage just knowing which ones you have and haven't already gotten.

If the game added just a slight way to provide some high level hints about when one might be near, the process would be a lot more possible to complete without cheating.  That just strikes me as a more solid design.