The guns themselves are pretty good to be honest but the only viable scenario i've used them in is CQB sites.
I used to use one at my CQB site and on 3 shot mode, it never had an issue sailing the BBs across the 35m-ish length of the site. Personally, I had the GE 8878 and the adjustable stock made it very comfortable to use. The shells are fine to use but a lot of people opt for the adapter that allows use of a M4 magazine instead but, IIRC, you had to remove the loading door to make it fit.
If you're going to use one at a CQB site, getting a tracer is a great idea. 5KU makes a tracer that fits over the end of the barrel and is secured by three grub screws.