Like anything it depends very much on the amount of light needed over the layout. I have the 300 led 3528 strip lights for illumination of lower decks on my layout, for me it provides all the light I need & that is having just one row of them, the particular track heads from the upper & main layout area, down to the staging yards, & return loop.
Around 12 metres are directly under the upper layout & have black pull away curtains, for almost the entire run there is 2 tracks & the strips a glued using the stick on tape as provided & none have come away from the framework board at the side of the upper deck that illuminates that area. My only problems with it is that the upper deck is not as far spaced as I would like, but I had no choice.
There are many types of LED strip lights, the primary ones are the 3528, with both 300 & 600 leds, the next type are the 5050 with same combinations of LEDs. The 300 LED 3528 only need a 2 amp supply for each 5 metres, with a maximum of 15 metres recommended per supply & therefore soldered together in a continuous run.
There are then the RGB strip lights that can be controlled to simulate the various lights seen in a day, Night, being blue the colours of dawn, the bright midday light as well as dusk etc. They do require more power & while some people like them a couple of modellers I know who wanted those decided against them as they were not as affective as first thought, & needed a fair bit of wiring & more power to operate them.
There are also bright white, cool light & warm lights available which cover many situations, the choice of waterproof against non waterproof. I am an el cheapo & use the non waterproof types as I have no water issues in my layout, but if you live in a damp humid area then they may be worth trying.
I have attached a 50 metre LED blue rope light to the ceiling of my train room, a 6mx6m insulated garage, which is used for night time operations, a couple of sections have gone in it, after it was used outside for a Christmas display, I will be replacing that with 3 banks of blue 3528 LED strip lights across the ceiling which will provide more than enough light, we already have one larger layout area that has only two of those strip lights for the night time operation, but he is going to fit another one shortly.
The idea of the blue lights is to have the affect of a full moon, & creates a nice atmosphere when only those lights are on, as well as the houses, street, yard, depot & station lights are the only other lights that are permanently on, of course signal lights, signal boxes as well as the lights on the trains also operate.
Here is a link to the shop I primarily usehttp://www.ebay.com.au/itm/110759686769?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
They are very reliable, although sometimes the postage takes time, I have no problems in recommending them either. As another poster has said, it could be worthwhile buying one to try it out, I would suggest however trying both the 3528 as well as the 5050, you may need different power supplies. I have used different Chinese & Hong Kong Ebay stores without any worries, if a problem happens they are usually very good in solving problems.
Search here http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=DC