jja, Bott, and Jay Hurst will probably be your best sources on the board, but, my experience:
Generally, there aren't as many products or lenders for Jumbos - but that's slowly improving. Expect higher rates, but, some of the brokers might have better rate options. Credit scores will generally have higher minimums.
Some secondary lenders don't do jumbo - but I've seen some who will go so far as an in-house portfolio loan for borrowers with lower scores (higher rates but the borrower is expected to move to a traditional seconday market mortgage within say 12-24 months). One of our wholesalers just added a jumbo product this week so the market is growing.
How big a jumbo?
Some lenders have pushed the minimum loan size up slightly to be categorized as a "jumbo"
You might also see some market specific limitations
When you hit the $1,000,000 appraised value is when it gets a little "stickier" with some lenders - closing can take longer as they likely will require two appraisals. I've had what started as a supposed 18-20 day home equity loan suddenly become 45-60 days due to underwriting and appraisal requirements. So jumbos can cost a little more, you may have to pay for an additional appraisal.
As far as Home Equity side - lenders may limit home equity / cash out due to size if you are $1M+, some won't have a cash out option at all.
Side note on home equity if you think you'll need it down the road:
We went with a securities based line of credit for our home renovations and we'll refinance when completed (or just pay down and keep it or pay off entirely). We got a sub 3% rate. We didn't want to wait since we'd be bumping the $1M mark and new baby on the way and needed to start construction, and we didn't care for the HE limit. And of course once a cash out always a cash out so we avoided that.