First off, the high up choke point (1). This is where the jump pad in the biggest room almost lands you if you choose to boost at the top of the hop. If you are attacking into the smaller room with the bridge from the "outside" on the ramps, you will almost certainly lose unless you can get your whole team through in a second or so. There is far more room to maneuver "inside" and far more room to safely repair while still maintaining a line of sight on the doorway. Teams inside pushing out will at the very least disperse their opponents, if they don't eliminate 1 or two who try to escape down the ramp to the side or jump off to the eventual death pit below; it is very easy to push most of a team off the small ramps and onto the ground below, breaking them up for easier, prioritized kills before cleaning up those that fell all the way down.
Second, the dead end/library (2). In my experience, it's easier to get a team up the curved back path and past the good cover provided by the big sphere tanks. Basically, it's easier to push UP here. Trying to enter from the bridge will usually end with you getting ambushed from the wide sight lines and ample cover that smarter teammates will use while their tankier friends whittle you down immediately. Coming up from the back, though, is a wide wall/building that covers LOS if taken advantage of quickly, and can be well used for corner-kiting.
These two create a weird flow; though it is advantageous to both exit the library out onto the bridge to have immediate high ground, you put yourself at the risk of attacks coming from the large upper room. Both flows essentially meet up on the bridge (3), forcing players to either leave for the blue alley in the back, head to the double-level room through one of the two parallel paths that go up or down, or loop back around up into the library again.
If you're in the Blue Alley (4), go up. Going down to the base of it might be useful to help your teammates in a pinch, but you can expect enemies to literally get the drop on your both from the main room and the split-level inside room upstairs (5). Your chances are best if you go up to the top outside corner and head up the little ramp that appears to the left behind a small cover wall to the inside room; this gets you to the high ground quickly and hopefully allows you to take out mechs silly enough to try the double-back path.
From the top of the map, you can either push out to the main room, or back along the curved highway (6) down to the large split level room where one team spawns at the start of a match. Pushing down the highway will help not only in giving you surfaces for your splash weapons to hit, but for a niftier purpose. Certain castles (citation needed) were constructed with spiral staircases ascending in a clockwise direction; this ingenious trick of architecture allowed only the defenders to freely swing their sword arms. By the same token, secondary weapons (on the right of your mech) fired while descending the curved ramp will hit the wall to the left a whole lot less than the other team will with their secondaries on the same side as the wall.
This split-level area at the bottom of the curved ramp is easiest to escape through either of the two thin parallel paths (7) that connect the upper and lower levels to the bottom level of the largest room. From here, your team can push out two different ways, but the enemy has to push in through a single choke point (8) at the base before having their forces split up by the two paths.
tl;dr follow these stupid arrows on this map when playing Uptown and your team is gonna just stomp n romp.
Here's a pic that should explain it all more clearly than I can. Red arrows are flow of traffic, blue arrows are smart flanking routes that are risky but keep the flow going if done quickly, and green Xs are just places you should never be.
If anyone can clarify what I've said, tell me I'm outright wrong, or at least give memorable names to these dang rooms, please, feel free. It's also interesting to note that that stage probably has such unique flow because it can't possibly support MA or Siege. I'm not actually a big fan of the map, but it has good concepts that don't show up in more symmetrical levels.
Edited by comic_sans, December 13 2013 - 02:07 PM.