I've been running a similar system for quite some time, and it's worked very well. It does, however, require some bookkeeping, so I'll warn you in advance. I've decreased treasure I give out by roughly 10%, and completely banned +stat items. It works out about the same, though a little better-rounded. Anyway, as follows:
Code:
Level Point-Buy Value LA +1 Point Buy
--------------------------------------------------
1 28 20
2 29 21
3 30 22
4 31 23
5 34 24
6 36 26
7 38 27
8 40 29
9 44 32
10 47 34
11 50 36
12 54 39
13 58 42
14 63 45
15 67 48
16 72 52
17 77 55
18 83 60
19 88 63
20 94 68
Instead of flat stat bonuses being accelerated, I've set it up so they actually gain more point-buy value as they go up levels. This allows for a fairly balanced progression - while players still tend to focus on one or two abilities, especially as they get higher level, it is sometimes more beneficial to increase a low stat than raise an already high one higher (due to the increasing point buy costs.)
Several things of note. I allow point-buy points to be saved from level to level - unlike feats, skills, and ability score increases, they do not need to be spent all at once. That does allow for the characters to raise a single stat multiple times, though they'll usually have to save up for several levels at a time if they wish to do that. Also important is the fact that point-buy values are calculated before all modifiers - including racial mods and the like. Thus where the bookkeeping comes in - it's important, when increasing scores, to remember that "oh, right, I have a +2 racial Con bonus, so it's only three points to raise, not four." That sort of thing.
Lastly, I still grant a flat +1 ability score increase at the normal levels, which, like racial bonuses, is applied
after point-buy value is determined. All in all, the system works quite well, inasmuch as it allows heroes with stat totals roughly as high as in the core rules, but without carrying lots of magic items devoted to it.
[Edit] Oh, right! The LA column. I saw a suggestion regarding that on the boards recently, and incorporated it into my system. I allow players to choose an LA+1 race at first level, but they have fewer points to spend increasing their stats. That continues over the 20 levels, so that they are always behind, ability-wise. Running a few examples up, it seemed an adequate compensation, for both sides of the divide.