As with all PV arrays, indeed all technologies, new products enter the market, and products become more cost efficient over time. This has been true of the mounting kits with inset kits (ie those that sit into the roof, on the sarking or batons) become more price friendly. These tend to be fitted to new builds, or retrofitting roofs or those that are being refurbished ... we think they tend to look better when installed with matt black panels.
There are fitted within the build schedule and offer savings on roofing costs and labour. They effectively work like 'velux' windows, with the roofer tiling / slating to the kit, and then flashings afterwards. They look great and usually fitted with black panels to reduce visibility. Below is just a couple we have installed recently.