I'm attempting to route a board that is, essentially, a breakout for the LPC23xx/LPC17xx MCU. I've never routed anything approaching this complexity before, and I have a few areas of concern. I know that a four-layer PCB would be optimal, but I'm a hobbyist, and turning this into a four-layer board would make this as expensive as commercially-available options. I've based my design on a couple of proven two-layer commercial boards, so I know that it is possible to make this work. First, this is the mostly-routed board (ignore all the USB machinery on the right, I haven't even decided for sure whether to include it) (also, I know the silkscreen is horrid, I haven't worked that out yet):
1) One area of concern I have is the length of traces between the MCU and crystals (one is for the RTC, the other is for the MCU). They're no longer than either of the boards that I based my design on, but I would like a bit of validation.
2) Another concern I have is decoupling. I know that, in general, there is no such thing as too much decoupling, but in this case, I'm short on space, so I haven't decoupled ALL of the VCC/GND pairs (there's a lot!). Both of the boards I based my design on have only 2 decoupling caps, and I have three, so I may be good there. Should I work to get at least one or two more in?
3) I've worked quite hard to provide a nearly-unbroken ground plane on the bottom layer. It's broken only in a couple spots, one for the through-holes (which I think should actually be pads) on one of the crystals, and the other is the largish route for VCC to the MCU. Is my ground plane solid enough?
4) Power distribution was a particular problem for me (see my previous question here). In the end I chose to pour a large fill under the MCU, and hook it up to the VCC pin with a large trace. Is this an acceptable strategy for power distribution? If I was working with a 4-layer board, I'd use a whole layer for VCC, but I want to stick with 2-layer for cost reasons.
Overall, how have I done here? Is this likely to boot up, or should I head back to the drawing board?