Whoever renovated it did an excellent job, really impressive design, sound was decent too.

I went to Bush Hall in Shepherds Bush for the first time a couple of weeks ago to see Soundtrack of Our Lives and was quite impressed with that place too.

Beautiful chandeliers and the ceiling reliefs and plush curtain backdrop made it very warm and atmospheric, great for photos.
Sound was probably more suited for semi-acoustic or orchestral shows rather than a full on rock gig though.

http://www.high-barn.com/thehighbarn.html

Worth keeping an eye on as they occasionally pull in a Massive-friendly name. Glenn Tilbrook, Charlie Watts, Kim Richey et al.

Can't beat it, if it's not raining and the music's good, eg Raconteurs/Vampire Weekend last year.

A great deal of effort has gone into getting the decor just right so it resembles a rundown old theatre cum bingo hall. It needs to be preserved for future generations of music fans - preferably in another country far away.

I would say the Embassy Rooms on Tottenham Court Road. Lots of carpet on the walls and a general air of civilized debauchery.

we went to Hem there years ago and they had table with candles on them it was really nice. Like the roundhouse too the staff are polite.
I like somerset house as an outdoor venue on the 2 occassion I've been for sigor ros and blue nile the summer evening gigs have been great, the slope of the quadrangle helping people see and the archtecture gving something to look at (for SR the clock timing match one of their gentle songs perfectly) and you get to walk over waterloo bridge afterwards score.

Never been but it looks glorious.

Went to see The Lucksmiths last night at "Neu Club" - and am still not sure how I feel about the venue.
It was all seated, at tables, like I'd imagine some kind of Las Vegas show to be. Table service for drinks, perfect view, decent sound, no smoking..... but was it a "proper gig" - I'm still not sure.
http://www.neuclub.es

is a fantastic venue, as that picture above shows. Intimate, great sound and adverts for apples, oranges and potato merchants on the balcony. You don't get that in the O2 enormodome.

Is the Philharmonic Hall in Liverpool, an art-deco masterpiece that's also designed to be as near perfect acousticly as possible. Going there is always a pleasurable experience, even if the act you are going to see is crap (yes, Lighthouse Family, I mean you)

http://www.liverpoolphil.com/content/AbouttheHall.aspx

is the main auditorium at Oran Mor in the west end - an old converted church with a beautifully painted ceiling and stained glass windows.

Went to see Emiliana Torrini there two weeks ago and there was no need to light the stage - the sun coming through the coloured glass was enough of a lightshow.

Images here -

http://www.oran-mor.co.uk/images.php

How could I forget the Union Chapel in Islington, wonderful setting for the stage in front of the stained glass windows, great acoustics for orchestral/semi acoustic shows (it's not a rock venue by any means).

Word of warning - better to avoid going to gigs there in the winter as sitting on a wooden pew while wearing a jumper, jacket and gloves is hardly a comfortable experience - and then there's the outside loos...

http://www.unionchapel.org.uk/index.php

Never thought I'd end up with a list of 'venues to see' next to my 'bands to see'.