There are pros & cons to LDON v. other zones, so it usually comes down to your play style and goals.
I have several characters who have done little or no LDONs (I started prior to POP expansion) and 1 that spent most of levels 23 to 49 in LDON.
LDON advantages in my opinion are:
1. Ability to find group, while my cleric and chanter have no problems finding groups, most of my other characters (I 2 box) can spend a whole evening with LFG on without finding one. LDON gives you a ready made place to find a group.
2. Augs - if you want to augment and tailor your existing equipment, you need to do LDON. Along the same lines, there are some really nice items only available from LDON merchants which require LDON points.
3. Experience is steady (though no where near as good as it used to be), especially compared to camping a rare spawn.
4. Fixed time limit adds excitement as opposed to endlessly killing the same camped mob.
5. The adventure stone quest/storyline can be interesting as you complete each camp series (which forces you to eventually move on to other camps).
6. No camp fights or KOS.
Downsides of LDON
1. Time consuming in that you really should figure on a 2 hour plus roundtrip between forming group, finishing, and splitting loot.
2. Coin Loot at higher levels is not as good as some other places (HG is Rathe for example).
3. LDONs do become somewhat redundent after doing many in the same theme.
4. While you need to learn group skills for LDON, tactics in LDON do not universally carry over to regular EQ.
5. If all you do is LDON, you really miss out on a lot of the EQ world.
Like a lot of things, if you do both in moderation, that is often the best method.
For 40s characters, I liked Unrest Basement, Spirocs (on same island as ogres) in Tim. Deep, Mts of Rathe, and LOY expansion areas. Hope this helps.
PS if you dont like LDON adventures, joining a guild will greatly improve your chances of finding a group by expanding your friends.