Analysis complete
Whoogh! That was a lot of numbers.
OK, first, here's the raw data :
http://patriot.net/~glurker/DnD/Analysis/spelllprog.html
There are some pretty hefty graphics on that page, so it will probably take a while to load. (In fact, unless you're on broadband, you probably shouldn't bother...)
Basic upshot: The feat in its current form seems to produce the smoothest curves. The semi-spell casters gain a little more benefit from the pair, since they can gain multiple metamagic spell slots per level from it, while the pure spellcasters will only gain one.
Final numbers represent something very close to the maximal progression, as I calculated as if the character spent all of his epic slots on the two feats. Practical spell progression will be much less than this. Even at this "rapid" pace, spell progression is about twice as slow as non-epic levels.
Cleric:
____0__1__2__3__4__5__6__7__8__9
20__6__5__5__5__5__5__4__4__4__4
30__9__7__7__7__6__6__5__4__4__4
40_10__9__7__7__7__7__6__5__5__5
50_10__9__9__8__8__8__7__7__7__7
60_11_11_11_10_10_10__8__8__8__8
Wizard:
____0__1__2__3__4__5__6__7__8__9
20__4__4__4__4__4__4__4__4__4__4
30__7__6__5__5__5__5__5__4__4__4
40__8__8__6__6__6__6__6__5__5__5
50__8__8__8__7__7__7__7__7__7__7
60_11_10_10__9__9__9__8__8__8__8
Sorceror:
____0__1__2__3__4__5__6__7__8__9
20__6__6__6__6__6__6__6__6__6__6
30__9__8__8__8__7__7__7__6__6__6
40_10_10__8__8__8__8__8__7__7__7
50_10_10_10__9__9__9__9__9__9__9
60_13_12_12_11_11_11_10_10_10_10
Druid:
____0__1__2__3__4__5__6__7__8__9
20__6__5__5__5__5__5__4__4__4__4
30__8__7__6__6__6__6__4__4__4__4
40_10__9__9__8__7__6__5__5__5__4
50_11_10_10__8__7__7__6__6__5__5
60_12_11_10__9__8__8__7__7__7__6
Bard:
____0__1__2__3__4__5__6__7__8__9
20__4__4__4__4__4__4__4__0__0__0
30__7__6__6__6__5__5__4__1__1__1
40__8__8__7__8__6__5__5__2__2__1
50__9__9__9__9__8__7__7__3__2__2
60_10_10_10__9__9__8__7__4__4__4
Paladin/Ranger:
____1__2__3__4__5__6__7__8__9
20__3__3__3__3__0__0__0__0__0
30__2__2__2__1__1__1__1__1__0
40__4__3__3__3__2__2__1__1__1
50__7__5__4__4__3__3__2__2__2
60__8__6__5__4__4__4__4__3__3
So, now that the numbers are up, opinions?