I deliberately didn't specify, but here's the difference between carry-over and not:
If you *don't* carry over, levelling up, getting a new Sperk, or acquiring a new class is tantamount to shooting your load after the advancement roll. Character advancement is strategic because you have to balance the capabilities you have with the level you are.
If you do carry over, you can level up, get a new Sperk, or acquire a new class *in addition to* other improvements. Character advancement is more tactical because you can always draw from your IP pool to get what you want, when you want it.
Personally, I don't carry over, and as a result, PCs spend the first few advancement rolls on improving key Abilities or getting the odd Perk or supplementing their Mana pool. After PCs get to reasonable plusses in their key Abilities, they decide to level up or get Sperks until about 4th- or 6th- level, then they go back to improving Abilities, getting powers, or maybe getting a new class.
If you allow carry over, you might consider letting characters spend an IP for some in-game benefit (cf. Bennies in Savage Worlds).
When writing Chimera, I wanted to give players advancement options. Because character level affects all sorts of subtle things, it's important, but the system allows you to get other improvements outside of level (I had a 3rd-level Veteran with Fight +6, which is arguably worse than a 6th-level Veteran with Fight +3, but a lot of that depends on the group's playing style and how the GM works the campaign).
All this said, I'm interested in how your groups spend their IP.
Cheers,
-- Erin
The Chimera RPGSimple Rules. Unlimited Options.http://www.welshpiper.com/