I've been using DiMarzios in all my 7-strings for years. I still like them but I decided to try to push the envelope a bit with some custom boutique pickups from Lollar and Vintage Vibe. I've been just thrilled with both of these pickups and I highly recommend both. These are both available direct from the manufacturers for anyone who's interested.
The Vintage Vibes are blades that many of you have seen on the photos I've posted of our recent bubinga 7-string. They're true P90 single coils with blades instead of screws. They're incredibly clear with a great P90 growl. I don't believe there's anything similar. The fit was a little iffy. They were a bit big for the rings although if you're doing a direct mount, they did fit the route with no difficulty. In either the neck or bridge position, they do have the usual single coil hum, but in the middle position running both pickups, they are absolutel drop dead slient. Pete Biltoft ar great at custom winding and he'll do any output level that you request. They are available with black, tortoise, and MOTO fronts. The price is about $160 for the pair.
The Lollars are in my new personal Swan LN7. They are based on his Imperials, which are a high quality PAF style pickup, but they are underwound for a lower output level. That produces a bit more clarity and a tighter low end. Jason is a great pickup maker and these are simply the best 7-string humbuckers that I've ever played. They are balanced, clear, and warm. I never play with distortion, so I can't really tell you what they'd sound like with a lot of gain, but I've always felt that if a pickup can do clean tone well, it can do anything else and thes pickups do clean tone just incredibly well. Jason built these for me with tortoise front to match the binding and I'm sure that he can also do some other fronts as well as the usual black. Like Pete, he can also do a variety of output levels, but I have a feeling that these pickups would get too dark if you wound the much brighter. You'll have to check with Jason Lollar for a price on these pickups, but his standard 6-sting Imperials are $300 for a pair, so expect to pay a pretty hefty premium.
Here are links to both companies sites for anyone who's interested.