I was surprised by how much I've used my DFA100mm. I was pretty sure I'd be all over macros and close-ups, but I have a few friends who spent the bucks on expensive macros only to have them sit in a cupboard unused, so I was very hesitant to spend that much. After over 7 years, it's easily my most used lens and what I paid for it now seems like peanuts spread out over time.
Optically, I'd say my da14mm was a pleasant surprise. It's not widely regarded as terrific so I wasn't expecting anything awesome (it has a few vocal supporters, but not a large fan club like many other lenses
). I found a used copy for a decent price, and have to say it exceeded my low expectations especially when it came to sharpness.