I am thinking about adopting Brendan's Simplified Spell Progression. I'll use it unmodified for both magic-users and clerics (I have always allowed clerics to have one 1st level spell at 1st level) and combine it with Ritual Spellcasting Variant 1 and 2. Spell memorization is thus simplified without sacrificing access to other spells (which may be cast ritually with a considerable increase in casting time).
One aspect of the simplified spell progression I really appreciate is the fact that it can be used to refer to a spellcaster's level in-character and actually be relevant in the game world. Depending on the setting, it may be common knowledge to everyone or possibly just to those with magical training that a spellcaster's level refers to how many spells can be held in the spellcaster's mind at one time. "She's a sorceress of the fifth level? Why, she can do five magical things every day with the snap of her fingers!" In my campaign, it will also be known that spellcasters commonly carry scrolls that enable them to cast even more spells (thanks to Holmes Basic), and that even without memorized spells and scrolls they can still use ritual magic. Some of Telecanter's Vancian Spell Ideas (namely #16) about magic items with their own spell slots that can be used by a magic-user to increase spell capacity is particularly useful here and fits in well with many fantasy settings in literature where objects often hold much of a spellcaster's power.
Overall, I think the combination of simplified Vancian magic and ritual magic will make magic-users more competent at low levels, less ultra-powerful at higher levels, and generally more enjoyable to play.