Thomas M.
Yelp
A gallery housed in two separate buildings (about a 5 minute walk from each other, on opposing sides of the same street) - one of them very much worth visiting (Modern I), the other one - well, not so much.
"Modern I" features the "traditional" modern art, which means: mostly works from the early to mid-20th century. So, not actually very modern at all. Which is a good thing, if you love figurative painting and not-so-abstract abstract painting - or, in short: *real* art. Which is why you should visit this place first. It has much more to offer - both qualitatively and quantitatively - and scores much lower on the pretentiousness scale. There are also temporary exhibitions (a major one on the late works of Roy Lichtenstein when I was visiting in early July). But the permanent exhibition is mighty impressive in itself (see my photos). And you can take photos of ALL pictures and sculptures. Ain't that nice?! Expect to spend around 1.5 hours there.
And then there's "Modern II" across the street. There's always a temp exhibition for which you'll have to pay an amount of money that's not really proportionate to the quality of said temporary exhibit (which is true of *all* major UK galleries, from Tate Britain, Tate Modern to Manchester etc). See, I caught the pretentiousness bug there. I could just have said: It's not worth the money. Sounds harsh, but there it is. Other than that, there's a rather tiny permanent display of some works which could have easily been shown in "Modern I" (say, Picasso, Dali, etc) - just 2 rooms, and a café and a shop. 25-30 minutes max for the permanent display.
The walk from city centre is about 30 minutes (off George or Princes Street), which is just fine when it's not raining. The permanent galleries are always free of charge. Since there are attractive parks and installations on either side, you may also feel tempted to just relax there for a while.
So, 5 stars for Modern I, 3 for Modern II. Makes 4.