The following assumes the Seraphis upgrade is accompanied by the Jamtis addressing scheme.
- Massive improvement in ring size (privacy improvement).
- Increased modularity of transaction protocol (easier upgrades in the future).
- New wallet tier allowing full view-only wallet functionality without spend key. 1
- New wallet tier allowing fast light wallet syncing with greater privacy than existing solutions.1
- New address scheme adds first-class support for embedded signatures to prevent man-in-the-middle attacks.1
Wallets will synchronize much faster thanks to view tags and other performance enhancements.
- New seed format (Polyseed) will be 16 words and will embed the wallet restore height, streamlining user experience.2
- New wallet tiers add complexity.1
- Users will need to generate new addresses.
- New addresses are longer.1
- Transactions will be slightly larger.
- New seed format may confuse users restoring older seeds (however, older seeds will still work). 2
Overall, it is very clear to me that this is a massive step forwards for Monero and its users. Better privacy, better performance, and a better user experience after the dust has settled.
Edit: I have been corrected, view tags are not part of Seraphis. They will be implemented sooner.
1 Specific to Jamtis, not necessarily Saraphis.
2 Not specific to Jamtis or Seraphis, but will likely gain traction as part of the same update.