I have a 220 ultimate (here it is on leather), the bracelet brother to the 104 ultimate.
It's a great watch. I have one of the early version so the LSWISSL is too close to the 6.
Major flaws with the watch;
1] LSWISS L, however this was fixed later on as you can see the pic of the spare dial I picked up with the correct spacing
2] Blue AR
3] Poor Lume
4] Crown is too close to case, and too beveled.
The Ultimates have 'I' serial. During this year they were in transition from open '6' to closed '6'. If you're so inclined DSN sells open 6 dials, you can compare in the pics. There is some mystery as to the crownguard. I have seen I 220s serial with both thick and thin crownguards.
I have bought some parts to mod mine. A dial with better spacing, a spring-loaded T crown. The only mod installed to my watch thus far is AR by fineDD. Next step is to get a dial lumed and install the new crown.
Just make sure when buying the 104 you get LSWISSL spacing like the pic of the dial by itself. It shouldn't be touching the 6.
Great choice of watch OP. But, the ultimates are expensive, modding even more so.
EDIT: The ultimates differ from the cheaper ones by having a good magnification on the cyclops, good datewheel and good dial.
My opinion on the watch? I like it very much. It feels like a quality piece and there is a nice weight to the watch. It's my favourite Panerai. The concentric circles @9, the mix of brushed and polished surfaces, the sausage dial, the date and the fact it's an auto. Unless you're willing to mod it, or buy premodded from the likes of Vaccum or Goin, I'd look at another watch, however. I have one of the recent 177Ls and it's a better watch for less money and doesn't require modding like the 104/220.
tl;dr
Definitely for those who see the 104/220 as a 'grail'. But better value can be found elsewhere.