LA hurts a lot more early on than later on (even if you aren't playing by the LA-buyoff rules).
+2 LA if you're starting at 3rd level is a death sentence most of the time, due to you having the HP, saves, BAB, and skills of a 1st-level character. It's generally not worth it.
+2 LA if you're starting at 9th level is considerably more OK, as long as you accept that you're essentially a 7th level character in every respect that matters.
A good rule of thumb: if the LA is going to be less than one-third of your total character level, it's going to be fine unless you're playing the party's main caster. That being said, if your group isn't very into optimization, some stuff (like a Half-Fey Sorcerer) become considerably more viable, since the LA acts as a nice handicap.
That being said... I doubt low-mid op groups will let you come to the table with a template, since they look cheese-y.
That being said, a Lesser Aasimar Paladin 2 with the Serenity feat and the Saint template is fluff gold, and would be reasonably solid in a 4th level party.
That being said, that's because Saint is amazing; if the Saint template was a two level class with a Commoner chassis, I could still see people dumping levels into it.
Actually, that's a good rule of thumb for templates - if you could see someone taking X levels of Commoner to get the template's benefits (where X is the template's LA), then it's good, and you could get away with having it be more that 1/3 of your character level.
Similarly, for a race with LA - if you could see yourself taking all the levels in a class X levels long, where X is the sum of its RHD and its LA to get the same benefits... then it's doable.
For example, an Ogre would be the equivalent of starting with a Half Orc, and taking 6 levels to just get a size increase, +10ft base land speed, +5 natural armor, a +8 to Str, a +4 to Con, and a +2 to Wis, with a further -2 penalty to Dex, Int, and Cha.
Would you take 6 levels in a class with one good save, poor BAB, and less than 2+Int skills for that?
