>Ooo! What levels is it good for exactly? Like mid 30s?

I went there at 30 and I'm within a bubble of hitting 35 tonight. I'm a
casual player (couple of hours a night at most) and have been there for
about 3 weeks now. Like you, I had been in Frontier Mountains doing the
giants, but it was quickly becoming FarmQuest, with everyone after Loops.
Dalnir (on my server at least) has less than 20 people in the zone at peak
times - you'll find mostly casters and monks there. Casters because of
their self-bind and monks because there's some nice loot for them.

The first floor is good for high 20's (at a push) to 33 or so. I'd stay
there for now until you find a regular group you're comfortable with... that
first trip down to the 2nd level can be a bit daunting. On the first floor
you'll find Ravenous Nibblers (pure melee), Gyrating Goo (melee but have a
strong poison DoT) and various Coerced beasties such as Gnomes, Goblins,
Iksar, Erudite, Tier'Dal and Dwarves. Most of them are casters, so have
Rhythms handy or get interrupting them with Pixie Strike.

The second floor is an absolute joy from 32-37. I'm 34 and everything still
cons blue. I've been grouping with a 38 necro and most of the Kly (Sarnaks)
were still blue to her. There's some excellent loot to be had there too,
but I'm all about the exp right now. :) Notable beasties are the Imprecator
himself (he drops one of the Ancient Coins for the Tambourine quest), and
Lumpy Goo (who drop Graven Sandals and Fighting Batons). The Imprecator
room is an absolute blast once you break that spawn cycle.

One thing to note about Dalnir is the non-aggro mobs. Some of the Nibblers
and Goo will happily let you stroll past. It helps to learn which ones and
where are non-aggro.

I'd recommend getting a good map of the place - try Allakhazam's for some
links.

Good Luck!

Kyrisha