It was pretty decent overall. Their representative was patient and responsive and I met him three or four times, spending about five or six hours in total, during which he answered all my questions, before I decided to go with HDFC. Of course, your mileage may vary on this front, since it depends on the individual in question. Generally, if you give them a sense that you're seriously considering them, they'll be more responsive and forthcoming with information.
Processing fee, I don't really remember - something like Rs 3500? Think it might have been waived off, as part of some promo. In any case, it's small enough that it's not something I would waste time haggling over.
The initial interest negotiation I didn't go very hard. I think he committed to 8.10%, saying he'd need to check with his superiors etc for lower, and on the day of disbursal/signing, "surprised" me with 8%. Obviously that was his figure all along and the only question was when he would offer it. This figure, of course, was a few rate hikes ago.
Other charges, I don't remember the specifics, but they were all on par with other lenders. And there were no surprise hidden charges revealed at the last minute. I asked them to be upfront on those and they were, 100%.
The only minor negative I can talk about is that they insist on the home insurance being from HDFC Ergo, and not any other GIC.