This could sound very depressing, and the person who actually attended the talk had thought they were damning statistics. However, I thought they were actually rather cheering because the implication is that he's very good at weeding out the manuscripts that he knows he's not interested in for whatever reason - subject matter, genre, writing style, author approach. For him to take on half - half! - means that he's good at spotting 'his' thing.
And that's what you want, an agent who thinks you're 'their' thing. You don't want to work with someone who doesn't believe in you. You don't want to work with someone who has to have their arm twisted in order for them to take you on. You want the agent who thinks your book is fab, the one who is bursting with enthusiasm to sell it, the one who utterly believes in your work.
And it's also encouraging for anyone who has received anything other than a standard rejection. Yes, you're one of the rejected, but the final 200 out of 4,800 doesn't sound so bad. You're in the top 2%! You've been picked out as worth of special merit, but this time - and with this agent - you're not moving on to the next level. However depressing, it's also a strong sign you're on the right lines.
Rejection is tough. Of course it is. But we all go through it. The writer who has never been rejected on the road to publication is a rare beast. I possess a letter from one agent who told me not to bother with writing as I was wasting my time. (I had a good publishing deal with a Big 6 publisher a few months later, so not entirely wasting my time...)
Take heart! Push on through the rejection, and try again. Try better.