Power
The power of the characters is likely to increase somewhat. This is
mainly due to players not selecting abilities they don't want or don't
think they will use.
Spellcasters
Spellcasters and/or magical abilities may become more common. This is
something to watch for. Glaive prices abilities on their usefulness, not
their rarity. Thus immunity to disease (fairly much useless in most
campaigns) is very cheap, although it is quite rare. The characters
shouldn't be overpowered simply by using Glaive, but they may have
abilities the DM would prefer they didn't.
No classes
On the surface this seems completely obvious. Glaive is a skill based
character creation system. It also means no _social_ classes either. A
paladin is not as strictly defined, nor are any of the other special
classes (druids, bards, specialist mages, etc). At character creation the
DM should be careful to define if a character is a member of that group
for the purposes of social convention.
For example, a character with good fighting skills but also some spell casting abilities. Are they are paladin, a priest or neither? This is for the DM to define. I would classify them as a paladin if they had the paladin's code restriction, or a priest otherwise. If they are a paladin or priest they should belong to an order. If they don't, why do they have any priest abilities?
Glenn Butcher / knight