While Nigel makes a good point, I wanted to add my own experience in this area. I've done a lot of design from 400 MHz to 6000 MHz and can attest that lumped reactances (ie. discrete inductors and capacitors) are much more convenient and practical to use at 900 MHz when compared to distributed (transmission line) circuits. However, as Nigel teaches, layout is supremely critical and the smaller surface mount components are essential. By smaller, I mean 0402 inductors and capacitors and while 0603 will work ok, why bother as it is only slightly harder to work with 0402 than with 0603 and stray reactances are less significant with the smaller parts. Once you become familiar with how "long" is too long a pcb trace at these frequencies, it all becomes fairly easy to successfully build your circuit. Often, once you have your pcb in front of you, a bit of tuning is necessary to optimize a circuit and it is very easy to swap from one value of inductor or capacitor to the next.
In designing commercial equipment the point where the advantages of using distributed reactances (transmission lines instead of discrete or lumped capacitors and inductors) exceeds those of using lumped elements is rather vague but in my experience it might be around 4000 MHz. This depends on your priorities and can vary from 1500 MHz o greater than 6000 MHz. Much of my last five years in design has been in the 5000 to 6000 MHz range and we still use lumped elements in most cases for interstage impedance matching, although it can be tricky. At these frequencies, for example, the length of an 0201-size chip inductor has to be compensated for when doing a series matching inductance. I have also found that, at these frequencies, it is best to purchase the lowest tolerance parts.
One benefit of using lumped elements vs distributed elements is that you can finish your circuit and begin production more quickly. You can also get away with lower performance pcb substrates too. Disadvantages include the problem of variation or tolerances, where pcb traces may be better controlled than discrete component values. PCB area, and so overall circuit size, will be larger with distributed elements. In commercial products, and especially consumer items, product size and time-to-market are very important so lumped elements are popular in, for example, mobile phones and wifi gear even though these operate at 1.7 to 6 GHz. Admittedly, these high volume consumer goods don't use much pcb copper at RF anymore as almost all the RF circuits are within one or very few RF ICs.